Reservoir re-housed, historical artifacts moved or rare environments relocated. Examples include the temples of Abu Simbel (which were moved before the construction of the Aswan Dam to create Lake Nasser from the Nile in Egypt), the relocation of the village of Capel Celyn during the construction of Llyn Celyn, and the relocation of Borgo San Pietro of Petrella Salto during the construction of Lake Salto. Construction of a reservoir in a valley will usually need the river to be diverted during part of the build, often through a temporary tunnel or by-pass channel. In hilly regions, reservoirs are often constructed by
Prince Sadruddin Aga Khan Nations Educational, Scientific and Cultural Organization (UNESCO) in 1958, and became the Executive Secretary to its International Action Committee for the Preservation of Nubia in 1961. This initiative brought together archaeologists from Eastern Europe and the West at the height of the Cold War. The construction of the Aswan Dam threatened ancient Egyptian treasures including Abu Simbel, the temples of Philae and Kalabsha, and the Christian churches of Nubia. He would later describe it as "one of UNESCO's great achievements" because of the challenging historical context in which it took place—in particular the ongoing tensions in the Middle East and