Llansteffan Castle sits on a much older Iron Age promontory fort, proving Llansteffan has been inhabited for several millennia. The hill where the castle stands commands the River Tywi estuary. The hill would have been stripped of trees so that foot soldiers were vulnerable to attack by archers. The original earthworks can still be seen and were used as part of the modern castle's defence system - the castle proper rests within the earthwork rings.
The castle was built by the Normans after 1100 as part of their invasion of Wales and granted to the Marmion family before passing to the de Camvilles through marriage.
It was captured by Maredudd ap Gruffydd in 1146 against the forces of Maurice FitzGerald, Lord of Lanstephan and his brother William FitzGerald, Lord of Emlyn who were the leading Norman settlers of the region. The castle was retaken by the Normans in 1158. Llywelyn the Great recaptured the castle for the Welsh in 1215 and taken back by the de Camville family sometime after 1223. The castle fell to Llywelyn ap Gruffudd in 1257 but returned to the de Camvilles by the 1260s.
The castle was captured twice by the forces of Owain Glyndŵr in 1403 and c.1405. It was recaptured by Sir John Pennes in 1408. The castle was later granted to the Crown and the two-tower Gatehouse was converted into a residence.
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.