Linnanmäki (Swedish: Borgbacken, colloquially Lintsi, lit. 'Hill Of The Castle') is an amusement park in Helsinki, Finland. It was opened on 27 May 1950 and is owned by the non-profit Children's Day Foundation (Finnish: Lasten Päivän Säätiö, Swedish: Stiftelsen Barnens Dag), which operates the park to raise funds for Finnish child welfare work. In 2023, the foundation donated €4.5 million, and so far has donated a total of over €130 million to this cause. Linnanmäki is the oldest and most popular amusement park in Finland. It has many rides of different types and sizes, and of the all Nordic amusement parks, Linnanmäki has the most rides in relation to the number of visitors. It also has other attractions, including arcades, games, kiosks, restaurants and an outdoor stage on which different performers appear in the summer. The park is open from spring to autumn; the opening day is around May Day and the closing is in the third week of October. Linnanmäki is visited by about a million guests annually. In August 2006, Linnanmäki received its fifty-millionth visitor.