Toruń Fortress (Fort IV)

Toruń Fortress is a ring of 19th-century Prussian fortifications encircling the city, and Fort IV is the one section built and preserved well enough to walk through, which is why most visitors come here. Built in the 1880s, Fort IV opens up kilometres of brick corridors, barrack rooms and moats, so you can move through the underground passages rather than just look at earthworks from the outside. People visit for the guided tours, the history events staged in the forts, and the cool, dim atmosphere of the tunnels themselves.

Fort IV is the best-preserved of the forts and the one adapted for tourism, so it is where a visit usually centres. Inside you follow long brick corridors between barrack rooms, cross or look down into the moats, and pass through the underground passages that give the place its character. The scale is the surprise: what looks like a low grassy mound from the road holds a network you can spend a good while exploring.

The full fortress is a ring of Prussian works thrown up in the 19th century, counted among the largest fortress complexes in this part of Europe. It runs to around 15 main forts plus dozens of smaller supporting works spread around the city's edge. Fort IV, from the 1880s, is the piece kept in tourable condition, but standing in it you get a sense of how much larger the whole defensive system once was.

This appeals to anyone drawn to military history, brick architecture or simply atmospheric underground spaces. The forts are popular for guided tours and history events, so going with a guide is often the best way to understand what each room and corridor was for. The passages stay cool and dim, so bring a layer and sensible footwear, and check the fort's official channels for current tour times before you set off.

Fort IV sits in the ring around the city rather than in the centre, so it pairs well with a day that also takes in the medieval core. Many travellers spend the morning among the Gothic streets of the Old Town and save the fort for a change of pace, swapping brick townhouses for brick tunnels. See the Toruń guide for how to combine the two into one visit.