"Every part of Egypt is interesting and curious,
but the only place to which the epithet beautiful can be
correctly applied is the island of Philae... "
Robert Curzon, from 'Visits to the Monasteries of the Levant', 1834
This island, originally known as 'P-aaleq', meaning 'The Remote Place', was situated just above the first cataract of the Nile river on what was then the border of Nubia, and was the centre of the cult of Isis, one of the most important goddesses in ancient Egypt.
The reasons for the islands importance for the cult was that it was believed that this spot was where Isis found the heart of Osiris after he was murdered by Seth, and that after retrieving his ruined corpse, she buried him on the nearby Island of Bigeh.
The first temple to be built on Philae was that of Amasis Khunimbre in around 550 BC, who built the original Temple of Isis. This structure was improved over time, firstly by Nectanebo I, and subsequently by a series of Ptolemian emperors. The completed shrine consisted of an Outer Court, accessible to the pilgrims who gathered from all over Egypt give offering to Isis. This structure surrounded an Inner Court which was comprised of the Mammissi or Birth House, the fabulously decorated Hypostyle Hall, entry to which was reserved for the priesthood, and the Inner Shrine, which contained the statue of Isis, which was only to be looked at by the High Priest during his daily rituals.
The Temple of Isis was not the only place of worship on the island, with Ptolemy VII building the Temple of Hathor, the Temple of Arenauphis, built by Ptolemy IV as well as Temples dedicated to Horus and to the Emperor Augustus to the west of the main structures, as well as the Nilometer, where the river's levels were constantly watched. To the north of the main buildings lay the Chapel of Imhotep dedicated to the Vizier and Chief Architect of King Zozer, Imhotep.
in 500AD the Roman Emperor Flavius Anicius Justinianus, ordered that this network of temples were to be closed, in so doing destroying the last home of ancient Egyptian religion and hieroglyphic knowledge.
Philae was submerged when the Aswan Dam was created in the 19th century, sinking 2500 years of history under the waters of Lake Nasser.
Sources:
http://www.philae.nu/philae
www.powerup.com.au/~ancient/philae.htm