Isegran is the first place in Fredrikstad mentioned in history. The Earl of Borgarsyssel, Alv Erlingsson, also called MindreAlv, had a small fortress on Isegran in the late 1200s. In the 1670s, the island was fortified with a large battery platform, Isegran tower, and later a small fort was built to protect the river. Until 1685 Isegran was the royal shipyard for the danish-norwegian fleet and during the Great Northern War, the island was the naval base for Peter Wessel Tordenskiold. The historic island can be reached via the Kråkerøy bridge or with the city ferry.
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.