... started out as a construction site. I was trying to build a demolition-themed map with exploding dynamite packs on the walls, crumbling ceilings and oil on the floor where every player is equipped with USP and a Para (thinking back this is pretty awesome. I want to revive that project if I can). The prototype build for that wasn't a lot of fun though because players would just stay away from the dangerous parts and snipe each other with single shots. I realized that the project needed a lot of work and quit it out of boredom.
A few hours later, I had had some more ideas about construction sites floating around in my head (I was trying to create a condemned-styled HL2 SP map at the time), so I sat down and mapped away. After a ground floor with a few obstacles and concrete shacks was done, I wanted to make the map more exciting by having it take place on top of an under-construction skyscraper. I noticed I'd have to create an extensive city scenery in the 3D sky to make that believable though and just screwed around demotivated, but then I noticed that a big concrete wall I just had textured and formed might aswell be used as a dam.
About two hours later, I ended up with the final map. I went on spending about 3 days trying to enhance it and improve lighting and color correction but was never content with the results, so I opted to release it like it is now.
The utter fortitude of this maps layout showed a second time when I thought to myself that I could really, really make it look better, but then just ended up adding and deleting stuff for another three days, finally causing me to accept its sturdiness and leaving it be.