Complex sentence: Pistiros was a major trading center of ancient Thrace, an emporium as much as a town, located near the Hebrus river (now the Maritza), near what is now Vetren, Bulgaria.
Split into simpler sentences: Pistiros was a major trading center of ancient Thrace, an emporium as much as it was a town. It was located near the Hebrus river (now the Maritza), near what is now Vetren, Bulgaria.