Mšeno Reservoir, reservoir in Mšeno nad Nisou, Jablonec nad Nisou, Czech Republic

The Mšeno Reservoir is a large body of water near the town of Mšeno nad Nisou, surrounded by forests and gentle hills. A substantial dam holds back the water, and its structure provides walking paths while the water offers space for boating and fishing activities.

Built between 1906 and 1909 by the Prague firm Franz Schön a synové to plans by Otto Intze of Aachen, the dam answered the floods of 1897, when 345 mm of rain fell in a day at Nová louka. Because the Mšenský potok catchment was small, Intze added two adits: the 632 m Pasecká from the Lužická Nisa and the 1,800 m Loučenská from the Bílá Nisa. The works cost 4,238,190 Austrian crowns.

Locals call it the Jablonec Sea, and the reservoir is the largest urban water reservoir in Central Europe. The Sluneční lázně open-air baths, built in 1927 to Josef Ulbrich's design, stood on the left bank until a fire destroyed them on 17 August 2022. Non-motorised paths run across the dams between the three basins.

The area is easy to access with simple gravel or dirt paths running around the water. Visitors will find facilities like toilets, showers, and picnic areas nearby, especially at popular beach sections.

The reservoir is fed not only by the Mšenský potok but also by two tunnels from the Lužická Nisa and Bílá Nisa, added because the stream's catchment was too small. The Pasecká tunnel is 632 m long and empties into the reservoir at the so-called Cikánská zátoka; the Loučenská tunnel, driven partly by hand and partly by an American boring machine, measures 1,800 m.