This was my first real attempt at diorama terrain. As a base, I used pink extruded polystyrene foam (XPS). In hindsight, this was a huge mistake, and knowing that helped a ton when planning my third diorama. I had always wanted to make my own riverbed, as well, but had no prior knowledge of what materials to use, so I ended up using layers of clear Elmers glue thinking that would do the trick. Instead, it pulled at the base, causing it to warp. Another lesson learned as I was later introduced to the magic of epoxy resin for my third diorama.
The two things I actually like that came out of this were my sand, gravel, and grass basing, and my painting of the rock faces. The techniques I used for those things on this have ended up being the same ttechniques I've used on every base and diorama I've made since.
Lastly, this was my first time really using cheap clay to try to mold something when I carved out and baked the bridge stones. They came out okay and served their purpose, but yet again thay ended up being a nice precursor to my later clay efforts like the sandbag walls in the third diorama. Maybe you can see the pattern here. The third diorama spawned from my desire to redo this thing and do it well. I like to think that's my way of learning from mistakes and knowing I can do better ever time I try again.