La Platte Mare is a simple megalithic chamber with a single capstone dating back to the Chalcolithic or Early Bronze Age (2500 - 1800 BC). Early drawings show that some stones have been disturbed. Traces of a surrounding circle of stones 5m in diameter are no longer visible. One stone has a curved row of 12 cup marks though only 7 are visible above ground. A few metres away are the remains of another possible cist or chamber.
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.