How to prevent people cutting through the woods

[Stone Teran]

I own some apartment buildings in a rough part of town.  The side is next to some woods and we just had a break-in on the apartment on the very end.  I want to put up some kind of fence to prevent people from coming out of the woods, breaking a window and carrying the loot back into the woods.

All my good ideas (tall fence, razor wire) are prohibited by the city.  A 6' fence might help slightly but most kids can hop those easily.  The area is too shady to allow much in the way of thorny plants.  What else can I use to keep the outside thugs out??