La Pedrera ( meaning 'The Quarry' ) aka Casa Mila in Barcelona is one of the main Gaudi residential buildings and a most imaginative house. The present owner - a foundation - opened the building to visitors (selected areas, including the roof!) and has developed a big variety of cultural exhibitions and events. In 1984, it was declared a World Heritage site by UNESCO. If you have been to Barcelona, you have for sure visited it ! .