Kilcashel Stone Fort is a double court cairn and National Monument located in County Mayo, Ireland, 800m southeast of Kilmovee. The last surviving member of three stone forts in the area, it's estimated to have been constructed between 2,500 and 500BC.
Kilcashel Stone Fort is 30 m in diameter; the stone wall is 5m thick and 3m in height. A souterrain is located inside, as well as a bullaun and the sites of two collapsed houses.
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.