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
Egyptian temple from the distorting effect of additional construction. Many temples, known as hypogea, were cut entirely into living rock, as at Abu Simbel, or had rock-cut inner chambers with masonry courtyards and pylons, as at Wadi es-Sebua. They used much the same layout as free-standing temples but used excavated chambers rather than buildings as their inner rooms. In some temples, like the mortuary temples at Deir el-Bahari, the processional path ran up a series of terraces rather than sitting on a single level. The Ptolemaic Temple of Kom Ombo was built with two main sanctuaries, producing two parallel axes that run