The Caverns of Thracia is considered by many to be a classic old school adventure from none other than Paul/Jennell Jaquays. While this might be true the actual maps in the adventure are somewhat confusing. This has been documented in various places and is not something new that is being pointed out. A good clarification of some of the interconnections of the maps can be found here.
Not that radical of a difference but the DM version has some more detail/info than what's shown in the published version. At least the old/original that I have. From what I'm given to understand the maps have been re-done and are much clearer these days in the newer version for sale. The first level map has been posted in more than a few places, so I'm not really giving anything away here.
A good level 1 treatment of the map/adventure can be found here if anyone's interested.