Haskovo (Хасково) — go see the KDK club, worth having some beers with a friend
Hissar (Хисар) — a nice little town a bit north of Plovdiv, known ever since Roman times because of its mineral springs. The central parts of the town are surrounded by an impressive city wall from Roman times, which is still in good shape. You can easily visit the Balkan mountain range and Koprivshtitsa from this base.
Plovdiv (Пловдив) — the nation's second largest city which boasts a lovely shopping promenade and many parks, an ancient city with a preserved amphitheater, and many "revival" style Bulgaria homes. Also make sure also to take a side trip to Bachkovo Monastery which is about an hour away.
Stara Zagora (Стара Загора) — with more than 8000 years of history, this is one of the oldest continuously populated places in Europe. Center of booming industry, remarkable cultural life and numerous tourist attractions, though it is the linden trees which give the city its character. Don't miss the Roman Villa Mosaics, the Neolithic Dwellings, the Regional Art Gallery, the countless coffee-shops and art-galleries, which give the city the feeling of a small Paris.
Elhovo (Елхово) — Elhovo is a Bulgarian town in Yambol Province, located on the left bank of Tundzha river, between Strandzha and Sakar mountains. The town of Elhovo is a center of civilizations since ancient times in the lands along the river of Tundzha.