Itemtest

itemtest.bsp from Team Fortress 2, a popular map for testing mods and expectedly, items. A fun little sandbox area to play in, surprisingly. There are no invisible walls, so you can hop the fence or go inside of the room with the green glass. Just keep in mind those areas aren't exactly going to be detailed because you weren't supposed to go there originally.

Thanks to Maranara and Tabloid I actually know how to do lighting somewhat now, so thank you.