Dagstuhl Castle ruins overlooks the newer Schloss Dagstuhl in the valley below, which is historic but has been converted for use as a conference centre. The castle was founded by Knight Boemund of Saarbrücken sometime before 1290, probably for Bohemond I von Warnesberg, Archbishop of Trier. The name derives from the German word for roof, 'Dach', because of the roof-like shape of the hill on which the castle stands.The castle ruins have been archaeologically explored and were improved for public access in 2004.
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.