The city hosts the Polish Academy of Sciences, National Philharmonic Orchestra, University of Warsaw, the Warsaw University of Technology, the National Museum, Zachęta Art Gallery and the Warsaw Grand Theatre, the largest of its kind in the world. The reconstructed Old Town, which represents examples of nearly every European architectural style and historical period, was listed as a World Heritage Site by UNESCO in 1980. Other main architectural attractions include the Royal Castle and the iconic King Sigismund's Column, the Wilanów Palace, the Palace on the Isle, St. John's Cathedral, Main Market Square, as well as numerous churches and mansions along the Royal Route. Warsaw possesses thriving arts and club scenes, gourmet restaurants and large urban green spaces, with around a quarter of the city's area occupied by parks.