Mine is the Bloom from Torment: Tides of Numenera. I love the fleshy bits. I love the everyday gruesome horror becoming an everyday thing for the people who live there. I love the literally organic surroundings. It’s just by far my favorite location in any game ever. :)
Fallout 2’s Enclave oil rig (Poseidon?) is pretty cool. I like how the guys who built the original oil rig put spooky faces on the big pipes, really shows an appreciation to their craft.
If you had the power to customize your piping you too would put a face on it! :P