Plainburg Castle - the family seat of the Counts of Plain and a symbol of Großgmain - is one of Austria's oldest castle ruins and offers a magnificent view over Großgmain and the surrounding mountains. All that remains of the original structure are the outside walls, with a thickness of 1.4m and standing to a height of over 5m. A short climb rewards the visitor with the opportunity to stop and rest awhile at the viewing platform overlooking Großgmain. Before it became the seat of the Counts of Plain, the mountain was a Celtic burial ground during the late Bronze Age around 1200 BC. Some time later, in about 1100 AD, Count Werigand of Plain built Plainburg Castle.
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.