The construction of the strong walls surrounding ancient Pharsalos, reinforced with towers and gates, commenced in the late 6th century B.C. The city flourished during the 5th and 4th centuries B.C. Visitors to the area can currently see 19 of the 23 total towers that have stood tirelessly along the perimeter of the walls for centuries, and which are part of the few remaining elements of the ancient acropolis, as Byzantine period conversions are mainly being restored. The acropolis gained a new wall during the reign of Emperor Justinian, incorporating certain elements of the older wall, while it continued being used in the post-Byzantine period.