Ten original maps from Team Fortress 2 have been added to the updated Source developer kits for modders to get their hands on, so go nuts.
For beginners it's a chance to poke around, for veterans it's a chance to poke around and point out flaws, most likely. More content is planned to be stuffed in the Source kits later on.
"...we're releasing an update to the Source SDK that includes the .vmf source files for many of the official TF2 maps. This is something we've wanted to do for a while, especially as we've been growing the range of game modes in TF," Valve .
The poor maps thrown to the wolves are Lumberyard, Ravine, Badlands, Dustbowl, Granary, Gravelpit, 2Fort, Badwater, Goldrush, and Hydro - please be gentle with them.
"Our plan is to get more of our TF content source out in the SDK, so look for more maps & model sources in the future." See I told you, I wasn't telling big fibbers.