For the first time in years, Prague residents and visitors will be able to step into one of the capital’s most unusual underground spaces.

On Saturday, September 20, Pražské vodovody a kanalizace (Prague Waterworks and Sewers) will open the so-called Cizinecký vstup beneath the Old Town Hall, a hidden chamber where the city’s main sewer line begins.

The chamber lies directly under Old Town Square, only steps away from the Astronomical Clock. Few realize that beneath their feet runs Sewer A, one of Prague’s most important underground arteries, stretching more than three kilometers and channeling wastewater from central districts toward the treatment plant in Bubeneč.

Guided tours will run throughout the day, beginning at 9:30 a.m. and ending at 4:30 p.m. Each visit will last about twenty minutes.

The meeting point is at the door to the right of the Astronomical Clock. Entry is free of charge, but advance registration is required at www.pvk.cz. Online booking opened on September 1, and will remain available until Friday, September 19, at 11:00 a.m.

According to company spokesman Tomáš Mrázek, capacity is limited and interest is traditionally high, so those who want to explore this rare site should reserve early.

A Century-Old Masterpiece of Engineering

Sewer A carries wastewater from Prague 1, 2, 3, and part of Prague 5. It collects flows from streets such as Celetná, Železná, Melantrichova, and Malé náměstí before joining larger collectors on its path to Bubeneč.

Constructed more than a century ago, the tunnel was designed by William Heerlein Lindley, the British engineer who created Prague’s entire sewer system. Built of smooth bricks with an egg-shaped profile, it ensures steady flow and reduces sediment build-up. Despite its age, the design remains fully functional, a testament to Lindley’s skill.

Prague’s Sewer Network in Numbers

The capital’s entire sewer network extends 3,904 kilometers. It is linked to 127,866 connections, which together add another thousand kilometers of underground lines. Daily operations are supported by 349 pumping stations across the city.

Most of Prague’s wastewater—about 92%—is treated at the central facility in Bubeneč. The remainder flows to one of 21 smaller treatment plants serving the outskirts.

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