Night One: I began documenting the construction after the foundation had already been lain.  Nothing huge has happened so far, but to explain a few of the techniques:

1. The entire project is mounted on hardboard (the stuff used for many clipboards).  It flexes a little, but is pretty durable while at the same time pretty thin and is easy to work with.  In this, my largest project to date, I did have a couple problems: note the cracking around the graveyard (bottom left), and the completed model is having some cracking in the front courtyard.  This isn't major, but something to be aware of.

2. The cobbles and tiles are all made from Hirst Arts blocks (HirstArts.Com).  I cut and sanded blocks to form the garden, graveyard, and the outer curve of the apse.  Everything was painted the same way: black spray primer, black brush touch up, then an uneven drybrushing of light grey.  The pattern on the floor of the cathedral itself was made by drybrushing white, and using sheets of paper to make crisp edges.  This color scheme is intentionally very bland; this is scenery, after all, and figures and armies should stand out against it easily, not compete for garishness; further, most surviving medieval towns are in fact fairly monotone, as stone was quarried from the same place.

3. The dirt areas were made according to instructions from Hirst Arts: they were filled unevenly with wet plaster, then sprinkled with dry plaster and then lightly sprayed with water to make sure it all set.  I would not do this again so thickly: the weight and water made the hardboard warp slightly -- not enough to be an issue, but enough to annoy the heck out of me and lead to all that cracking.  I should have done two or three smaller pours.

4. The stairs aren't painted.  They were too wet to paint with the other stuff, and you'll notice it takes me a long time to get around to finishing with them.  The figures are included for scale; I always keep a couple on hand (an elf and a dwarf in this case) to see how terrain is going to affect them -- problems seeing over walls, or being placed easily into nooks and crannies, are a lot easier to resolve during construction than after.
 

The same status, but without the half-completed outbuilding.  I was still very unsure if I wanted to use it, and this was part of my testing.  I didn't decide for sure until the very end, and I'll go more into my thinking on that later.
 
 

Again, most of this step (all but the nave and towers) I had already completed before I took a few months break from this project.  Again, however, it's simply a very lot of small steps and pieces.

1. All the walls and buttresses are made from foamcore.  Mmmm foamcore.  I use the black matte stuff because it paints up much better (it's like it's already primered!)  The buttresses were all made according to a pattern and I cut out a ton of them (several weren't used...sigh).  Everything else is just very carefully measured, and subjected to many test fits (such as this one).

2. To make the walls more interesting, I add holes (use the point of a pen or compass and poke a couple in places, like bullet holes), broken faces (cut a shallow, uneven depression not quite all the way through the wall), cracks (cut a narrow, angled groove in a spiderweb fashion, then sorta-mirror it with another cut about 1/8" away to make a V), and jagged edges (cut from one side at a steep angle, then from the other side, then make several notches along the top to give it a ragged look).
 

Close up of the nave.
 

Close up of the apse.  I raised this area to give a more interesting look, as though there were a crypt in the foundations here.  I used a combination of items to give it a proper lift.  You can also see I used a second piece of hardboard to form the floor of the entire cathedral.
 

Close up of the southwest wall, at this time the only place with series of buttresses (come on, two is a series!)   You can also see the huge hole I cut in the southwest bell tower to give access to a lower floor.  I didn't want to repeat this the whole way down, so access to the two lower floors of the bell tower was sacrificed to artistic conception.
 

Close up of the front.  Very boring.  This is the one part of the cathedral I would like to redo, particularly with added windows beneath the rosette.
 

Painted and gluing begun.  Now drybrushed, all the cracks and gouges stand out nicely.

1. Painting couldn't be simpler.  I use Apple Barrel paints (cheap water based acrylics, less than a buck a bottle).  I use a 1/2" brush from the hardware store (the wooden handled cheap type) to drybrush and stipple (simply tap with the end of the brush) to give a good, uneven effect.  First I do a coat of Beachcomber Beige (a light tan color) then a coat of white.  The two colors add a better illusion of depth and texture than just one.
 

Another angle of the same stage.
 

Gluing the nave and towers; these were large sections that had to be carefully placed and lined up very accurately, so I used clamps to force them into place.  Sometimes tools are more important than skill!  For all these stages I used wood glue; it dries faster than white, with a stronger bond, but slowly enough I can work with it.  Within about 5 minutes things are usually set well enough to work with.
 

Night Two: Glued the buttresses on the apse, and cut several more pieces to fit.  These will cover the unseen crypt and the arches will support the first roof and bracket the lower stained glass windows.  The first of many, many arches.  If you're thinking of doing a project like this, don't worry if you aren't good at freehanding these: by the time you're done, you will be!
 

The same work on the east side of the apse; here it's just stub buttresses, no arches (yay!)
 

Those very same arches painted and glued.  I have no idea where that gap with the glue came from -- I have photographic evidence just above that it wasn't there during the test fit!  Ah, the joy of large projects.  Things are finally taking shape, though!
 

Wood working!  The various floors of the tower and the balcony for the nave.  The doors, at the top, were completed during my first effort, and yes, they do open and close.

1. Floors are easy.  I use popsicle/craft sticks for almost everything.  Sketch out the size of area you want to cover, or use graph paper, and lay out boards until it's filled.  Put a couple the opposite direction to glue to.  I use pruning snips to cut the wood: very precise and sharp, no effort on my part.  Don't hold the wood in a stupid way and snip your own finger though.  I don't know about tears, but I definitely invested blood and sweat on this stage.  Break sticks to get a nice ragged edge, and then fit them in and cut the other end to length to make the edge keep a good curve.  Also, for effect, use an x-acto knife to cut a few sticks lengthwise, to the planks look uneven.  Do I need to say use wood glue?  No, I didn't think so.  When it's dry, either paint it or use my lazy method: brush on a dark water-based wood stain.

I want to point out again that while this may look complex, it's not.  Note that the only cut that wasn't straight was on the corner of the balcony: other than that, all you need to do is cut carefully and glue.

2. The balcony was a pure hell.  It doesn't look that exciting, but trust me on this.  The entire cathedral was a series of very non-complex, simple tasks done enough times to look really complex.  The balcony was not: I had to get width, angle, length, supports, breaks, etc. all right at the same time.  Anyhow, it was a pain, so just have pity on me here.

3. The doors were simple, but required fairly exact cuts.  The planks, tops and bases are all craft sticks.  The horizontal supports are coffee stir sticks from Starbucks.  The hinges are tiny balsa dowels from the craft store.  I glued everything together thoroughly and used a drill to make holes for the hinges (which have to be the exact right length...1/16" off is too much).  I'm not sure I would suggest this method for much: it was very time consuming for a small gimmick and they don't open widely enough for my personal taste.  For a couple key entrances, like this one, sure; but for a normal door, no way.
 

The woodworks stained and glued in place.  Note I used small bits of balsa as supports around the edges.  Normally I just use a craft stick turned on end, but I was feeling experimental.  Craft sticks on end are easier and better, is what the experiment found out, but these did work fine for my purposes.  The sad part is, half these floors will barely be seen at all once I have the front on.
 

The west door and balcony: I added a couple rails made from balsa wood.  The unstained bits of wood are just supporting everything while the glue dries. The columns are made from balsa wood, notched then painted just as the floor was.
 

Back to the big view: the front is now glued in place.  I also added several columns in the apse, which will frame the upper level of windows.
 

Night Three: I did a web image search for stained glass windows and found these.  They're simple enough to print out well, look appropriate (mmm, skulls) and after alot of stretching are the right size.  They were actually part of some vampire adventure setting, not a real cathedral.  I had them printed on transparencies: $2.50 each sheet, which is expensive compared to most of my materials (the entire cathedral probably uses around $25-30 in expendables) but well worth it for the effect.
 

The first level of windows is installed in the apse, and guess what -- more arches!  A LOT more arches.....

1. Windows were simple: cut them out from the sheet with a small (1/4" or so) overlap, and use white glue (so it'll be clear when it dries).  With the slow drying time and weak glue, I had to use weights to keep the windows in place.
 

A (unfortunately very fuzzy) close up of the exterior of the apse with the first level of windows.
 

The upper level of arches painted and installed, as well as another column to make the western apse a full gallery.  A center arch was also installed.
 

More arches installed to make a small gallery in the nave, and another arch for effect between the towers.
 

Night Four: Roofing  and the second level of windows added.  This is molded styrene, available from any train store.  It worked amazingly well; thick but flexible and easy to cut.  It was spendy, though: $10 for two sheets, and I used one for this project.  Not really much advice for working with it (this was my first time) except to measure twice, cut once.  Maybe measure three or four times, and cut once on a sheet of paper, then cut the styrene.
 

The roofing painted and glued (the pencil is holding it down while it dries) and the steps painted (finally! ...and way, way too white).  I also added stub buttresses and arches around the doors, and started filling in the blank spots where the building and fountain were going to sit.  I've also added another arch to the west transept: eventually I'll add a bit more roofing there, and another window.

1. I wanted to go for a fully oxidized copper look on the roofing (what they actually used) -- think the color of the Statue of Liberty if you don't stare at cathedral often.   I did a base of aqua, then dry brushed bright green, then did an ink wash with heavily watered brown Games Workship ink.  It doesn't look like the real thing at all, really: it came out way too bright.  I would suggest a black (not white) undercoat and cut both colors with white to make them more pastel-ish.  The brown wash worked well, though, to give it an aged, dirty look.  However, despite the screw up I like the color: the hitherto really bland building really needed a strong splash of color to help it stand out a bit and look more centerpiece-y.
 

A view of the roofing over the nave, and the new buttress at the bottom of the picture.
 

So, if you remember earlier I mentioned an outbuilding, and this was decision time: I've painted up the newly-added tiles, but I'm about to glue something, somewhere, on the exterior.    I've added a couple other buildings to show my dilemma.

I positioned the entire cathedral at a small (about 30 degree) angle, for two reasons: first, it allowed me to make the building a little longer while still having an open space in front, and second to break up the grid pattern that's created by my modular set up (all buildings on on rectangles some multiple of 6" -- up until now I've only made 12" x 12" plates, but this plate is 24" x 18").  However, to fully break up the grid I needed a road at an angle completely off-grid: thus, the idea to put a wedge-shaped outbuilding close to the edge, to create a narrow road paralelling the cathedral -- the above picture.
 

In this picture, you see the other option: instead of a narrow, angled road, there's an open area with a corner that instead reinforces the grid pattern.  Aesthetically, I hate this.

My opinion was shifted by a large number of factors.  First of all, everyone -- literally, every single person -- that I asked about it said to drop the little building, mostly followed with either "duh" or rolled eyes.  Also, the narrow road was TOO narrow: for wargaming, a 2" gap is hard to maneuver much through, and the exterior edge promised the potential for even worse, depending on what plate I put it next to.  Finally, and what really decided me, this is a centerpiece: it should be a stand alone item, without anything in the way when set as a display item.  Thus, the verdict: the outbuilding is toast.
 

Fifth Night: Basically completed.  Here seen from the northwest, I've glued the fountain, added flocking to the old garden and graveyard, made simple graves, and added a series of banners and carpets to make the exterior more visually interesting.

1. Fountain: Made from Hirst Arts bricks, painted black in the interior with an uneven green stippling, then filled with water effects.

2.  The textiles are made from linen paper and stamped.  The banners were cut with long ends to wrap around the poles (more of those craft store dowels, stained) and glued on the walls.

3. I won't go into the flocking (it's...flocking) but the tall weeds are brush bristles (from the same type of cheap wooden handled brush I mentioned above).

4. The graves are craft sticks, a base for a Reaper figurine, and bits from Games Workshop's skeleton boxed set (as are the decorations above the doors -- they're actually shield emblems).
 

From the southwest, with rosette and banners.  It's still too plain, but the banners helped it out a lot.  And yes, there is a very, very small copy of the 95 theses posted on the front door (can see it better on the layout pictures, two up).
 

From the southeast, the open area and graveyard.  The large grave still needs to be finished, and I'll add a wrought iron fence when I get inspired again.  Note the easy access to the entire interior from this angle: the basis of the layout.  A good view of the apse, as well, and all the windows.
 

Seen in context, dominating the profile of mini-Mordheim.  Note the elevated graveyard in the bottom right corner: the same style of black fence will go around the cathedral's graveyard.
 

Again in context, it's still surprising to me how much it dominates over all my other buildings -- they seemed large at the time!