La Sagrada Familia is one of Gaudí's most famous works in Barcelona. It's a giant Basilica that has been under construction since 1882 (that's not a typing error!) and it's not expected to be completed for between 30 to 80 years ( time for completion varies depending on different sources of information)
Much controversy surrounds the building of the Sagrada Familia. Today new construction materials are being used which, some feel, Gaudí himself would not have used.