Old Town Bridge Tower, Gothic tower at Charles Bridge, Prague, Czech Republic

The Old Town Bridge Tower is a 47-metre Gothic tower of quarry masonry faced with sandstone blocks, built on a square plan on the first pillar of Charles Bridge. Its eight-metre-wide passage is vaulted with a net vault whose keystone takes the form of a royal crown. A spiral staircase of 138 steps climbs an annex on the south wall to an open gallery with corner turrets and a steep slate roof.

Peter Parler designed this defensive structure in the 14th century as part of the medieval fortification system protecting the approach to Prague's Old Town. The building was later modified and expanded to meet the city's changing needs over the centuries.

The facade facing the Old Town is carved in three tiers: at the base, small figures on consoles show human failings; above the arch, the coats of arms of the lands Charles IV ruled, from Luxembourg and Moravia to Bohemia and the Lusatias, plus the Old Town's own shield. Higher up stand St. Vitus, Charles IV and Wenceslas IV, and four kingfishers in wreaths, the badge of Wenceslas IV.

The spiral staircase to the gallery has 138 steps and winds up an annex on the south wall. The gallery is open, with a parapet and corner turrets, so wind and weather are felt directly. The tower is administered by Prague City Tourism.

In the 1620s, heads of executed rebels were displayed on the bridge side as a warning to others, remaining there for years. This dark chapter is now an important part of local memory about the city's political struggles during that era.