10.12 CITY KEYSTONES

City keystones are used to limit how deep into a city improvements may be
placed. The keystones for each city are as follows:

Ashtan    : Entering the Main Gate of Ashtan
Cyrene    : The Cyrene Gates 
Eleusis   : Base of the Eleusian Gatehouse
Hashan    : Porta Aquila
Mhaldor   : The Gates of Mhaldor
Targossas : The Champions' Bridge