UDK - Unreal Engine Map File
This is a game map design file created by the Unreal Engine Development Kit (UDK) which is a popular free game engine currently developed by Epic Games. It saves the layout, textures and 3D objects used by a game map. It is also used to create the 3D worlds that Unreal games are played in. UDK files may also contain ambient sound location as well as the path information utilized by AI (artificial intelligence) players.