The Forest Kingdom is a dam reservoir on the River Elbe built in 1920. It lies at the lonely Tešnov in the cadastral area of Bílá Třemešná, 4 km upstream from Dvůr Králové nad Labem, in a narrow valley passing through Kocléřovský ridge. On the left bank there is the vast forest complex of the Kingdom, the rest of the old border forest, after which the dam was named.
The dam is unusual in Czech conditions with its highly aesthetic construction. Today, due to its uniqueness, it is a sought-after destination for tourists.
From 18. April 1964 is a dam with a power plant registered as an immovable cultural monument, from 1. July 2010 is a national cultural monument.
After the devastating 1897 flood that hit the Elbe valley to Pardubice, it was decided to construct two water works to keep the floodwaters - the Labská dam (near Špindlerův Mlýn) and Tešnovská (today's dam of the Království Forest). The documentation for the construction project was started by 1903 in the preparation of the Technical Department for River Treatment in Prague, led by the building board Ing. Josef Plickou. The construction took place in 1910-1920 (the first world war was delayed). The construction part was carried out by JV Velflík and the machinery was supplied by Fanta and Jireš (both companies also from Prague). The cost of building the dam was 4,7 million Austrian crowns. After the construction was completed, it was the largest water reservoir in the then Czechoslovak Republic.
The dyke is gravitational arc, bricked from the King's sandstone. The width of the dam in the base is 37 meters and in the crown 7,2 m. The length of the dam in the crown is 218 meters. The maximum height of the dam is 41,1 m, the depth at the dam is about 28 meters. The reservoir has a long 5,1 km and the maximum flooded area is 85 hectares (in normal operation 58,6 ha). As part of the dam, 1923 also has a hydropower station with the power of 2 × 600 kW. In 2005, turbines were replaced, a new power of 2120 kW. After the crown, the dyke leads roads of local importance.
The whole set of buildings is dealt with in a romantic, pseudo-gothic spirit. The crown of the dam is complemented by two gates with decorative towers. The cottage, standing on the right bank, reminds of a small stone castle with a dominant tower with battlements.
The tank may be named under names Forest of the Kingdom, Tešnovská (Těšnovská) to white Třemešná.