This 30 meters high rock hill was used as guard hill in the Middle Ages. If enemy ships were seen coming from the sea, fire was lighted to the hill to warn local people. After the great fire in Turku (1827), instruments and astronomical books of Turku University observatory were transferred to Helsinki.
The Helsinki astronomical observatory was built to the hill in 1834. It designed in cooperation by professor Friedrich Wilhelm Argelander and architect Carl Ludvig Engel. The observatory was among the most modern astronomical observatories of its time, and served as an example for several European observatories that were built afterwards. A separate tower was built in the observatory garden for the telescope designed for astrophotography. This building was finished in 1890.
At the top of the hill is is also situated Stigell’s monument Haaksirikkoiset (“shipwrecked”), erected in 1898. The sculpture is stretching to the west and increased the national spirit in the end of the 19th century.
Hluboká Castle (Schloss Frauenberg) is considered one of the most beautiful castles in the Czech Republic. In the second half of the 13th century, a Gothic castle was built at the site. During its history, the castle was rebuilt several times. It was first expanded during the Renaissance period, then rebuilt into a Baroque castle at the order of Adam Franz von Schwarzenberg in the beginning of the 18th century. It reached its current appearance during the 19th century, when Johann Adolf II von Schwarzenberg ordered the reconstruction of the castle in the romantic style of England's Windsor Castle.
The Schwarzenbergs lived in Hluboká until the end of 1939, when the last owner (Adolph Schwarzenberg) emigrated overseas to escape from the Nazis. The Schwarzenbergs lost all of their Czech property through a special legislative Act, the Lex Schwarzenberg, in 1947.
The original royal castle of Přemysl Otakar II from the second half of the 13th century was rebuilt at the end of the 16th century by the Lords of Hradec. It received its present appearance under Count Jan Adam of Schwarzenberg. According to the English Windsor example, architects Franz Beer and F. Deworetzky built a Romantic Neo-Gothic chateau, surrounded by a 1.9 square kilometres English park here in the years 1841 to 1871. In 1940, the castle was seized from the last owner, Adolph Schwarzenberg by the Gestapo and confiscated by the government of Czechoslovakia after the end of World War II. The castle is open to public. There is a winter garden and riding-hall where the Southern Bohemian gallery exhibitions have been housed since 1956.