Fort Saint Pieter in Maastricht, Netherlands

Constructed in the 18th century to defend the strategically important city of Maastricht in the Netherlands, the Fort Saint Pieter is a fantastical looking hexagonal construction full of tunnels and caves that, while imposing, only ever saw a single battle.

Built in what was once known as the "Iron City," thanks to its impenetrable defenses that lasted through multiple attacks on its strategic position, the fort was the answer to one of the attacks that broke the famous line. It was in 1673 that the French forces of Louis the XIV breached the walls of Maastricht on roughly the exact spot that Fort Saint Peter now sits. The French sacked the city, but the builders had learned their lesson. The angular defensive fort was built a couple of hundred years later.   

The hill-like stronghold soon came to be known as the tallest "mountain" in the area. The interior was a maze of tunnels and passages that connected to the famous marl caves that run beneath the city. The rows of gunnery windows and solid, thick walls proved their efficacy during another attack by the French in 1794, in which the fortification held strong against the siege. However this was to be the fort’s shining moment as it was not attacked again before being decommissioned.

After being abandoned for a number of years, the Fort Saint Pieter was restored in 2011 and is now open for tours. The damage from the 1794 attack was left intact as a reminder of the fort’s martial history.