Valletta contains buildings from the 16th century onwards, built during the rule of the Order of St. John also known as Knights Hospitaller. The city is essentially Baroque in character, with elements of Mannerist, Neo-Classical and Modern architecture in selected areas, though the Second World War left major scars on the city, particularly the destruction of the Royal Opera House. The City of Valletta was officially recognised as a World Heritage Site by UNESCO in 1980.