1. LA SAGRADA FAMILIA (Church of the Holy Family)

One of Antoni Gaudí's most famous works in Barcelona, the giant Basilica is Spain's top tourist landmark and has been under construction since 1882 -- and is still not complete. Work stalled after Gaudi's death in 1926 due to lack of funding and the fact that his designs were destroyed during the Spanish Civil War in the 1930s. It's now targeted to be completed in 2026 -- the centenary year of his death.