La Sagrada Familia
Construction began in the 1880s and continued through Gaudi's death in 1926 until 1936, when it was interrupted by the Spanish Civil War. Work continued intermittently from 1940 until the 1990s, when work accelerated to complete the cathedral by 2026.
This has proven controversial because the design is deviating significantly from Gaudi's original plans, which are on display in the museum in the crypt. There has also been controversy over the siting of a high speed train tunnel which passes very close by the foundations.
It is possible to watch the construction in progress as the cathedral is already open to the public.