The ground gave way behind him, closing off the tunnel with a gravelstream. Too familiar an event, but this time was different. In front of him, a track, a well maintained track it seemed. And a miners station, which seemed to have been abbandoned just recently. Steve was well and truly intrigued by this. "This is not normal, not at all."

He ventured forward, following the track, wary for using it, as tracks often tended to end up in horrible pits of lava. ANd for every block he stepped, the air seemed to grow denser. Whispers starting fading in and out of hearing, coming seemingly from the walls themselves. First faintly, but growing more audible with each step.

"An intruder..." "No, a stranger..." "Beware, stranger..."

A light, not from a torch, came into view, the fog of the tunnel clearing away. Out of the tunnel he stepped and in front of him... Something he had never seen before...

He had stepped in an enormous cave, filled with strange structures, hanging down from the ceiling, connected with a surprising amount of suspended walkways, with mineshafts protruding into the walls. "Not normal at all..."

Additional Notes

General Idea: An undeground ruin-complex, made by a maybe not so lost culture. Hanging from the ceiling of the cave, suspended in the air, connected with bridges.

At the moment, I'm laying out the outline of the structures.
At the moment, I'm finishing the exterior of the structures.
At the moment, I'm finishing interior decoration of the ruins and finetuning ambient lighting.
At the moment, I'm placing redstone and commandblocks.
As good as finished! Enjoy :D

Thoughts behind the build: As we are given a costum terrain to work with, the first thing I was thinking about was how I could create something big and complex without altering the terrain too much. The answer therefor was to build a suspended structure, as the ceilings of caves are too often forgotten about in many cases. My idea was to build a series of suspended towers, of which the basic form is based on that of typical medieval doomed buildings, with several tiers and sloping "roofs".

However, the terrain can be altered. I joined some waterways together, made some smaller springs that "form" those waterways and used several geological processes as inspiration for certain shapes and forms (like erosion, stalactite-formations and mineral depositing). Also, mines would be an important process, as an underground culture would rely on mines to provide in many needs, thus an extensive mine should be present and could be used to initially connect together the first suspended buildings (which will later on be connected via suspended walkways).

"But why would anyone build underground?" In my idea, the city is to serve as a safe-haven in times of great trouble, therefor the city should have at least 1 exit to the outside, but wait! Isn't that where you came from, where a gravelstream has sealed you off from the other side? Then, perhaps, there are 2 exits?

A download is available, but it is the most basic finish I have available atm. It will probably be expanded upon in the last days and probably I'll keep working on it once the contest is done. I have seen some really good aesthetic builds and only a select few good Adventure-builds ("Depths of Corruption" for example, by Xenocide).