Urkulu (1,419 m) is a mountain in the Basque Country straddling the border between France and Spain. The main feature of the mountain is the remains of a Roman tower topping the summit, erected in the 1st century BC. to commemorate the recent conquest of Aquitaine.
With the summit providing excellent views over the northern and southern slopes alike, it was used as a watchtower in medieval times.
The tower has a truncated-conical shape, measures 19.5 meters in diameter at the base and is 3.6 meters high. Its original height should have been 4.5 meters. The thickness of the walls is 2.6 meters and its interior is filled with the remains of the original stonework.
References:Goryōkaku (五稜郭) (literally, 'five-point fort') is a star fort in the Japanese city of Hakodate on the island of Hokkaido. The fortress was completed in 1866. It was the main fortress of the short-lived Republic of Ezo.
Goryōkaku was designed in 1855 by Takeda Ayasaburō and Jules Brunet. Their plans was based on the work of the French architect Vauban. The fortress was completed in 1866, two years before the collapse of the Tokugawa Shogunate. It is shaped like a five-pointed star. This allowed for greater numbers of gun emplacements on its walls than a traditional Japanese fortress, and reduced the number of blind spots where a cannon could not fire.
The fort was built by the Tokugawa shogunate to protect the Tsugaru Strait against a possible invasion by the Meiji government.
Goryōkaku is famous as the site of the last battle of the Boshin War.