The historic centre of Riga was designated a UNESCO World Heritage site in 1997. Many medieval buildings survive, among them the 13th-century Riga Dom (cathedral), the 14th-century Riga Castle (1330), and merchants’ homes and warehouses. The canal around the city’s Old Town was the fortress moat. Nearby, many elaborate facades in the Jugendstilartistic style testify to Riga’s wealth in the late 19th and early 20th centuries. Among the public buildings that were renovated in the 1990s was the National Opera, first built as the Riga German Theatre in 1863. The 14th-century House of Blackheads, damaged during World War II and razed in 1954, was rebuilt in 2000. Early 21st-century construction included high-rise towers, a hockey stadium that hosted the 2006 Ice Hockey World Championship, and the National Library, completed in 2013.