Underground Prague — Cellars, Tunnels and Hidden Spaces

Prague's street level is not where it started. Over centuries, the city literally built itself upward — filling in flood-prone ground floors with rubble and raising roads by two to three metres. The result is a second city beneath the pavement: a network of medieval cellars, baroque tunnels, and forgotten rooms that most visitors walk directly above without knowing.

We take guests into these underground spaces regularly on our Hidden Prague — Underground and Alchemy tour, and the reaction is always the same — genuine disbelief that all of this exists one staircase below the tourist crowds. Here's what's down there and how to see it.

Why Prague Has So Much Underground

The short answer: floods. Prague sits on the Vltava, and before modern flood controls, the river regularly spilled into the Old Town. After major floods in the 12th and 13th centuries, the city decided to raise the ground level rather than keep rebuilding. New construction went on top of the old — what had been ground-floor rooms became cellars.

This happened gradually over several hundred years. A Romanesque merchant's house from the 1100s might have its original entrance two metres below today's sidewalk. Some buildings in Old Town have three basement levels, each from a different century. The deepest spaces near the river date to the earliest settlement.

The result is that Prague's underground is not a single tunnel system like Paris or Rome. It's hundreds of individual spaces — cellars, passageways, storage vaults — connected in some places and sealed off in others. New sections are still being discovered during construction work and, occasionally, by accident.

Old Town Underground

The most accessible stretch of historical underground runs beneath Staroměstské náměstí (Old Town Square) and the surrounding streets. Several buildings on the square have Romanesque cellars that are open to visitors. You descend a narrow staircase and find yourself in barrel-vaulted rooms built from rough stone blocks — rooms that were once at street level, with windows that now face solid earth.

The official Old Town underground tour covers a route beneath several connected buildings, showing how the city was built up layer by layer. You can see the original Romanesque doorframes, the fill material that raised the streets, and in some places, the old well shafts that once served surface buildings.

One detail we always point out to guests: look at the walls where the original ground level meets the later fill. You can see a clear line — lighter stone below, darker material above — marking the moment the city decided to bury its own past. It's subtle, but once you see it, the entire concept of Prague's layered history clicks into place.

Speculum Alchemiae

Speculum Alchemiae is one of Prague's strangest stories. This Renaissance-era alchemist's workshop on Haštalská ulice in Old Town was rediscovered in 2002 when the Vltava flooded and water broke through a wall in the building's cellar. Behind the wall: a network of tunnels, a hidden laboratory, and a passage that reportedly connects to Prague Castle — though only a portion is open today.