When it opened in 1958, Moderna Museet soon gained a reputation as one of the world's most ground-breaking contemporary art venues. Housed originally in an old, disused naval exercise building, the museum's heyday came in the 1960s and '70s when it introduced Andy Warhol, Jean Tinguely, Robert Rauschenberg, Niki de Saint Phalle and many more to an astonished Swedish audience. The construction of Moneo's new museum building was completed in 1998, but it closed four years later owing to structural problems, including a mould infestation. The museum reopened in 2004 with a brighter interior, a more open floor plan, an espresso bar and - most importantly - no mould. Its collection of 20th-century art, featuring works by greats such as Picasso, Dali, Pollock and de Chirico, is arranged in reverse chronological order on the main floor. The terrace of the museum's restaurant offers beautiful views towards Östermalm. Though admission to the museum is no longer free, the '1st at Moderna' series on the first of every month offers a free look at a new exhibition.