Sluice Štvanice, Navigation lock in Prague, Czech Republic

Sluice Štvanice is a water step on the Vltava at Štvanice Island, at river kilometre 50.69. It consists of the Helmovský weir on the left arm and two parallel locks, 11 metres wide, in the left part of the right arm; a sports slalom channel lies to their right.

The lock chambers were built between 1907 and 1912 as part of the Vltava navigation works carried out by the Lanna firm, at the same time as Hlávkův Bridge. The works removed the island chain with its mills (Primátorský, Korunní, Jeruzalémský) and reshaped Štvanice. The lock was rebuilt in the 1940s and again in 1984–1987, when the slalom channel was added.

The weir's name comes from the Helm mills, which stood on the right bank from 1398 and belonged to the Knights of the Cross with the Red Star. Each year the weir's 12-metre log chute is opened for the Napříč Prahou – přes tři jezy swim, the only time it is used.

The best view of the lock comes from the nearby bridges or the riverside path, where you can watch it operate. The structure is freely accessible from outside and can be visited at any time, with the most interesting periods being when boats pass through the gates.

The sports slalom channel beside the locks was built in 1984–1987, and the weir's 12-metre log chute stays closed except during the annual Napříč Prahou race across three weirs. A stage of the original Francis turbine stands outside the Štvanice power station as a sculpture by Tomáš Šenberger.