Oslo houses over 20 theatres, such as the Norwegian Theatre and the National Theatre located at Karl Johan Street. The National Theatre is the largest theatre in Norway and is situated between the royal palace and the parliament building, Stortinget. The names of Ludvig Holberg, Henrik Ibsen and Bjørnstjerne Bjørnson are engraved on the façade of the building over the main entrance. This theatre represents the actors and play-writers of the country but the songwriters, singers and dancers are represented in the form of a newly opened Oslo Opera House, situated in Bjørvika. The Opera was opened in 2008 and is a national landmark, designed by the Norwegian architectural firm, Snøhetta. There are two houses, together containing over 2000 seats. The building cost 500 million euro to build and took five years to build and is known for being the first Opera House in the world to let people walk on the roof of the building. The foyer and the roof are also used for concerts as well as the three stages.