Work continued at a steady pace and in 1954 the foundations to support the Passion facade were started, based on several studies Gaudí had carried out between 1892 and 1917. After the foundations were laid the Passion facade crypt was built on them, and in 1961 a museum was opened in the crypt to provide visitors with information about the history and technical, artistic and symbolic aspects of the temple. The four bell towers on the Passion facade were completed in 1976.