The town changed its name not juts one. First it was known as Beroe, after that the Romans renamed it and called it Augusta Trayana. After the Romans it became Beroe again and later Boruj. Other names such as Verea and Irinopolis refer to the same place. The Ottomans called it Eski Zagra, from which the present name derives. The new name means Old Zagra. Of course there's also a New Zagra (Nova Zagora) not far from Old Zagora. Another common spelling is Stara Sagora.
The town is located between Plovdiv in the east and Burgas at the Black Sea coast. It sprawls along the southern foot of Sarnena Gora (Sarnena Mountains), which are the foothills of Stara Planina (Balkan mountains). When you cross the famous Shipka Pass in the north, you can easily get to Veliko Tarnovo in North Bulgaria, which is not so far away. South of Stara Zagora is the long Mountainous Thracian Plain.