Valletta's 16th-century buildings were constructed by the Knights Hospitaller. The city was named after Jean Parisot de Valette, who succeeded in defending the island from an Ottoman invasion during the Great Siege of Malta. The city is Baroque in character, with elements of Mannerist, Neo-Classical and Modern architecture, though the Second World War left major scars on the city, particularly the destruction of the Royal Opera House. The city was officially recognised as a World Heritage Site by UNESCO in 1980.