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
Kazimierz Michałowski were discovered under the "church of the columns". The second building based on the cruciform plan was also explored as well as a mosque which turned out to be erected on a former royal palace and not (as previously assumed) on a Christian temple. Polish archaeologists discovered also a baptistery. Since 1966 a Polish mission was performing parallel prehistoric excavations in the vicinity the village of Gaddar. Professor Michałowski did not excavate in Abu Simbel but along with a team of Polish archaeologists he took part in the salvaging of rock temples of Pharaoh Ramesses II, which were at risk