The Tregiffian Burial Chamber is a Neolithic or early Bronze Age chambered tomb. It is a rare form of a passage grave, known as an Entrance grave. It has an entrance passage, lined with stone slabs, which leads into a central chamber. This type of tomb is also found in the neighbouring Isles of Scilly.
The large stone grave, half of which was covered by a road in 1846, was, unlike Cornish quoits, for the most part covered with soil, with only the entrance exposed. From the edge of the site a passage, covered by four 3 m long stones, led to the 4-metre deep grave chamber. In front of the chamber, a cross-lying ornate stone, with cup-and-ring markings, formed a barrier. The original stone is in Truro, in the Royal Cornwall Museum, the local stone is a replica. Inside the tomb there was the chamber grave, which consisted of upright stones and a cover slab. Tregiffian probably formed a holy place with the Merry Maidens and other sites.
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.