Fort Napoleon in Ostend is a polygonal fort built in the Napoleonic era. It has recently been restored and is open to the public.
France had occupied the Austrian Netherlands (a territory roughly corresponding to the borders of modern Belgium) during 1792 and 1793 in the Flanders Campaign of the French Revolutionary Wars. During the War of the Fifth Coalition, Napoleon Bonaparte expected a British assault from the sea on the port of Ostend, and the fort was constructed in the sand dunes close to the mouth of the harbour in 1811. The British attack never materialised and the fort was used as for troop accommodation and as an arsenal until the end of the French occupation in 1814 when it was abandoned.
During World War I, the fort was used as accommodation for a German headquarters, and decorated with murals by German soldier Heinrich Otto Pieper. The heavy coastal artillery battery Hindenburg was stationed nearby. It was armed with four 280 mm guns of 1886-1887 vintage in heavily armored turrets on semi-circular concrete platforms. It was captured by the Belgian army in 1918.
The fort was also used as German artillery headquarters during World War II. After the war, it served as a museum and then a children's playground before falling into decay. In 1995, the fort was restored and opened to the public in 2000.
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.