At Zub: http://dayzdb.com/map#6.064.097

The main tower is hard to get past the initial entrance. You can't walk in, you have to "V"-step, and then you end up "land sharking" the stone floor. If you are lucky, the game decides that you are in the wong place after a while and pops you up to the floor, but it is a tad crappy as it is now.

(also it was not worth the effort as there appears to be no loot spawning there anyway)