Once when I was bored, I decompiled a map from Half-Life:Game of The Year just for fun. The map was c1a1e (the one when Gordon pushes the sample into the machine). I loaded it up into Hammer. I was amazed about how many invalid structures, wrong textures, useless structures, useless brushes and errors there were! I wonder if Valve were drunk when they built them! This is no offence to Valve or anything, but GOD! On the other hand, the errors were probably decompiler errors! WinBSPc is the most buggy decmpiler out!
{NOTE:I DID NOT DECOMPILE THE MAP TO STEAL ANYTHING! I JUST DECOMPILED IT TO SEE WHAT IT LOOKS LIKE IN IT'S ORIGINAL STATE WHEN VALVE WERE BUILDING IT!}