The impressive rectangular course of walls of Hisarja's fortress, erected in the 4C by Thracian stone masons, run for 2.5km, entered on the south side through a monumental gate known as "the camels" (kamilite). Thrace’s third city, Augusta (the Roman name of Hisarja), once stood within these walls. Today, the site is essentially occupied by a vast park (planted with acacias, magnolias, paulownias etc), criss-crossed by wide avenues (often pedestrian) and dotted with a few buildings.