The Old Fort The original fort built by the Mormons in  1855 consisted of an adobe enclosure, 150 feet on each side, with towers or bastions at the northwest and southeast corners.   The adobe building closest to the creek is the only surviving part of this structure.  The other walls you see and the bastion at the northwest corner are reconstructions.  The building was most recently used as a testing lab and office for the United States Bureau of Reclamation, which leased and renovated the building in 1929 during the construction of Hoover Dam.  The photo shows the lab in 1929.