The black, lattice-work spire of Riddarholmskyrkan is one of Stockholm's most distinctive sights, visible from all over the city. Construction on the church started in the late 13th century as a monastery for Franciscan monks. The church's benefactor, King Magnus Ladulås, is buried in the church along with 16 other monarchs, including Gustav III, Gustav II Adolf and, the last to be buried here in 1950, Gustav V. Since the 17th century, only two Swedish monarchs have not been buried here. Additions have been made to the church over time, in part to make room for more graves, since an estimated 500-1,000 people are buried in its floors and vaults - the floor consists almost entirely of grave-covering stone slabs. The southern wall was moved back in the 15th century, the tower was added in the late 16th century, and work began in 1838 on the current cast-iron spire after lightning struck the original. Colourful plaques of the Serafim order, which are awarded to Swedish nobility and visiting heads of state, decorate the walls of the church.