Haga Castle, Hotel and conference center near Lake Mälaren, Sweden

Haga Castle is a two-storey rendered stone house designed by Nicodemus Tessin the Elder in an Italian late-Renaissance style and completed in 1670. A broad open-air stair with a balustrade leads to the main entrance, whose recessed three-storey centre is topped by a lantern. On the lake side, pilasters divide the facade into five sections of two window axes each, and the coats of arms of the owner and his wife are carved in stone above the central portal.

Haga began as the medieval castle Marieborg on an islet at the Enköping River's outlet into Lake Mälaren; Ture Stensson (Bielke) moved the seat to the Gammal-Haga lands by 1425. In the late 1660s Gustaf Persson (Natt och Dag) had Nicodemus Tessin the Elder design the present main building, completed in 1670. The estate passed by inheritance until 1836, was bought by the Hotel and Restaurant Employees' Union in 1924, served as a mental hospital from the early 1940s to 1962, and reopened as a hotel and conference centre in May 1990.

The Swedish Hotel and Restaurant Employees' Union bought Haga in 1924 and turned it into a summer home for its members. The estate later served as a mental hospital from the early 1940s until 1962. Since 1990 the renovated buildings have operated as a hotel and conference centre, run since 2018 by the company Lyckorna together with Schenströmska herrgården.

The main buildings are reached from the north off riksväg 55 along an avenue of trees about one kilometre long, with the corps de logi placed on the avenue's axis. The grounds include the wings, the park to the south and the avenue to the north; the surrounding housing is a separate property. The estate has its own jetty on Lake Mälaren.

Between 1940 and 1962 the property served as a psychiatric hospital, a lesser-known chapter in its long story. This period shaped the building and remains part of its layered past.