This example of dense topography represents a mighty Dwarven stronghold -- either defended by the Dwarves, or perhaps abandoned by them centuries or millenia earlier and now held by Goblins. Does that sound like Moria (Khazad-Dum)? Maybe...
I had a lot of fun making this topography. First thing was to make the base map that would work. I could have just used black or brown fabric (sturdy duckcloth or canvas), but I found a really cool printed fabric from Spoonflower that I bought online. You can get swatches to test colors for relatively cheap. I had it printed on "Cypress Cotton Canvas" (one of their fabric options); when the bolt arrived, I cut it to size and sewed double-fold bias tape to the edge to stop it from fraying. Note also that this base map works great for Underdark armies (natural caverns and caves hollowed out below the sunlit world).
Here's how it looked when cut to size and edged with bias tape (below).
The next thing was to make a whole bunch of rooms (large open spaces). The idea here was the huge open areas inside the Stronghold -- rooms so large that a Balrog could stand upright in them, to choose a not-random example. I took a sheet of 1/8" MDF (coarse brown surface on one side, white on the other) and cut a bunch of rectangles out in 6MU x 8MU sizes ("small" terrain pieces in Triumph), and some more in 8MU x 12MU ("large" terrain pieces), and then I cut out some even larger pieces for the center area. The center two 16MU x 16MU zones have to be mostly clear open terrain, as described in the Fantasy Triumph rules.
After cutting the piece out, and in some cases beveling their corners (some or all) because having only rectangles is boring, I used a black Sharpie to draw pillars, cracks, edge walls, platforms, and the like. All decorative (they don't influence the game) but really cool looking. Then I splashed some Miracle Dip on them, let it dry, and done.
Following are some example pieces.
This piece is 8x8 MU. That makes it a "Large" piece for Triumph
Note the cool tile detail. I had a metal cooling rack for cooking that was a simple grid of perpendicular metal rods (thin ones, 1/16" or less). Place that down on the surface and draw the interior squares with an ultra-fine Sharpie and you get these nice tile shapes. Too much work to do the whole surface, so this room is in disrepair and you can only see the tiles in some areas.
In the Triumph rules you can have some edge pieces that are longer but less wide than regular ones. That works well for a huge underground stronghold. Here's a 4x12 MU edge piece ("small").
As mentioned above, but this one is 6x16 MU (a "large" edge piece). This can also serve as part of the central region (about which more later).
I'll have to go back and look at the dimensions for this one.
Simple rectangular columns, set diagonally to contrast with other rooms that have orthogonal columns.
This was a leftover piece, it is not quite square, something like 8x8.5 MU. I played around with the edge decoration for this one, using a scrap of wood from putting together some laser-cut wood kit. I never throw anything away.
This room is 6x8 MU, simple rectangle. You know you are a true mega-level nerd when you take a picture of the cracks in asphalt in your cul-de-sac while walking, so you can draw realistic cracks in your stonework for gaming. Which is what I did here. Aren't those some awesome cracks?
This is a 6x8 MU room with a central pillar (or maybe a fountain!) and lots of tile. I used the tiling technique metioned above, but here I only did every other tile. Still a lot of work. And I messed it up in one place. Oh, well.
When I was making the Crack room above I thought "hey, what if a big room was partially collapsed?" I took an 8x12 ("large") room and cut out a section with my scroll saw, made sure the size was still legal after the removed part, and here it is. Love it. And I've still got the cutoff piece, so I can add some rubble and stuff for an even nicer looking map.
Same as above, but with a 6x8 MU ("small") room to start before attacking it with the scroll saw.
As mentioned, Dense Topography requires that the center be mostly clear terrain. For this Dwarven Stronghold, that means a series of rooms that can be put together in any way I like (so long as they are still legal by the Dense Topo rules).
Here's one of the main ones -- a 12x16 MU room with a dais at one end.
Here's another room for the center region. I think this is like 8x16, or maybe 10x16?
Here's an example of a complete map with just two terrain pieces, both small (8x12) and the center area built up of rooms.
Here's another example, with a small room (attached to the central zone) and a large collapsed room, plus the passageway ("stream" in Dense Topography) that is allowed. As described in the Dense Topo rules it is possible to make a connection between the passageway and the central zone at their closest approach (with some other rules as well).
As I mentioned at the start, the cloth underlay could serve also for Underdark armies who would have natural caverns for many (or all?) of their terrain pieces. Here's the first one of those, cut out using my scroll saw. This counts as a "large" piece -- it fits within an 8x12 MU rectangle (diagonally).
I searched for and downloaded the National Speleological Society guide on drawing cave maps so I could use proper notation for flowstone and the like. Like ya do.