http://www.dakkadakka.com/dakkaforum/posts/list/8.page JForum - http://www.jforum.net http://www.dakkadakka.com/dakkaforum/posts/preList/706416/8981420.page http://www.dakkadakka.com/dakkaforum/posts/preList/706416/8981420.page GMT
For the actual buildings themselves and their interior you need to be looking at Art Deco architecture (the style of Rapture). Knights of Dice have some nice laser cut MDF stuff you could buy http://knightsofdice.com/store/index.php?main_page=index&cPath=51

As for the external, you basically need to simulate the bottom of the ocean, and I would expect that if you wanted to do it, you would be looking at sculpting lots of your own stuff. So that said, you could be using extruded foam to build the rocky shapes, and then probably aquarium plants for the vegetative stuff, on top of various puttys for sculpting.]]> http://www.dakkadakka.com/dakkaforum/posts/preList/706416/8981835.page http://www.dakkadakka.com/dakkaforum/posts/preList/706416/8981835.page GMT
http://antimatter-games.com/products-page/terrain/#store]]> http://www.dakkadakka.com/dakkaforum/posts/preList/706416/8981897.page http://www.dakkadakka.com/dakkaforum/posts/preList/706416/8981897.page GMT