Abergavenny Castle was established by the Norman lord Hamelin de Balun c. 1087. It was built to overlook the River Usk and its valley, and so guard against incursions into the lowland areas south and east of the town by the Welsh from the hills to the north and west.
The castle was then the scene of an infamous massacre. Over Christmas 1175 De Braose called Seisyll and his son Geoffrey to his castle, together with other leaders from Gwent, supposedly as an act of reconciliation. De Braose then had the men killed in the castle's great hall, in retribution for the death of Henry Fitzmiles. His action, including taking the men's land, resulted in sanctions: William was 'retired' from public life and the castle passed to his son, William. In 1182 Hywel ap Iorwerth, lord of Caerleon, ordered the destruction of Dingestow Castle and had Abergavenny Castle set afire in retribution for the murder of Seisyll. The attacks were made by Seisyll's relatives. De Braose was not at the castle when it was burnt, but 'most of his men' were taken hostage.
The castle was almost entirely rebuilt of local Old Red Sandstone, starting about 1190, to make it easier to defend. Five towers were built along the curtain walls, and a keep was built. The English and Welsh fought for control of the Welsh Marches and, during this time, possession of the castle alternated between the Welsh and English. In 1215, the castle was visited by John, King of England.
In 1404, during the rebellion of Owain Glyndŵr, the town of Abergavenny was sacked and burned by Welsh forces. The fortified, or barbican, gatehouse, may date from either just before, or just after, that date.
The castle, now in ruins, had a stone keep, towers, and ditch as fortifications. It also housed the family and army of the lord and had cellars, kitchens, a great hall, gatehouse, and a chapel, although it is doubtful whether any of the families treated the castle as their main residence. A curtain wall surrounded the castle.
The high, formidable curtain wall, dating from the 12th century, is now the most impressive part of the ruin. A 19th century lodge was built on the top of the motte in the 19th century.
The castle's museum is located in the 1819 hunting lodge on top of the motte. Amongst the museum's exhibits are a saddler's workshop and a Victorian Welsh farmhouse kitchen.
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.