Kovachevsko kale was a Roman city which lies 6 kilometres west of the Bulgarian town of Popovo. The Czech archaeologist Karel Škorpil called it Kovachoveshko kale, after the name of the nearby village, Kovachevets.
It is notable for its massive defensive walls which have a roughly triangular plan and enclosed an area of more than 40 hectares. The stone walls are fortified with 17 U-shaped towers. There are two gates, one to the west and one to the north-east.
The city is located on a flat terrain, naturally protected by rivers.
The strong 3.20 m thick walls were built between 308 and 324 AD during the joint reign of Roman Emperors Constantine I the Great and Licinius after the Gothic Wars of 250-269. The city was set on fire in the Second Gothic War of 376-382 AD. It was slowly restored until the invasion of Attila the Hun around 447 AD. Finally it was destroyed by the Slavs and Avars in the 580s.
Recent excavations by Veliko Tarnovo University have revealed a huge Roman building from the 4th century AD within the walls which appears to have been a horreum (i.e. a granary). It measured over 60m x 25m, though it has not been fully exposed. It had a massive double door of 2.4m width. The walls of the building are 1.3m wide reinforced with external buttresses. It had two stories and a basement and was constructed with opus mixtum. The granary was plundered and set on fire around 378 AD probably by the Goths.
An underground aqueduct built of clay pipes supplied the fortress with drinking water, descending from the northwest over several kilometres from Kalakoch hill.
References:The ancient Argos Theater was built in 320 BC. and is located in Argos, Greece against Larissa Hill. Nearby from this site is Agora, Roman Odeon, and the Baths of Argos. The theater is one of the largest architectural developments in Greece and was renovated in ca 120 AD.
The Hellenistic theater at Argos is cut into the hillside of the Larisa, with 90 steps up a steep incline, forming a narrow rectilinear cavea. Among the largest theaters in Greece, it held about 20,000 spectators and is divided by two landings into three horizontal sections. Staircases further divide the cavea into four cunei, corresponding to the tribes of Argos A high wall was erected to prevent unauthorized access into the theatron and may have helped the acoustics, but it is said the sound quality is still very good today.
Around 120 CE, both theaters were renovated in the Roman style.