Stockholm, the capital of Sweden, encompasses 14 islands of the vast Stockholm archipelago on the Baltic Sea. The cobblestone streets and ochre-colored buildings of medieval Gamla Stan, the old town, are home to a 13th-century cathedral, the royal palace of Kungliga Slottet and its underground armory, cafes and restaurants. Ferries and sightseeing boats shuttle passengers between islands, beneath more than 50 bridges. 917,197 people live in the municipality. Due to the city's high northerly latitude, daylight varies widely from more than 18 hours around midsummer, to only around 6 hours in late December. Despite its northern location, Stockholm has relatively mild weather, the summer average daytime high temperatures are 10–15 °C (68–77 °F). The average winter temperatures ranges from −3 to −1 °C (17 to 30 °F), spring and autumn are generally cool to mild. Apart from being Sweden's capital, Stockholm houses many national cultural institutions. Stockholm is one of the most crowded museum-cities in the world with around 100 museums, visited by millions of people every year.