One of the main sites visited by almost every tour to Egypt is what is billed as Philae, but Philae is actually a nonexistent island now buried beneath Lake Nasser.  The island was sometimes visible and sometimes not after the Old Aswan Dam was built, but was permanently submerged by the High Dam.

Philae is an approximate Greek rendering of the local name "Pilak" known from hieroglyphic texts and which may be Nubian in origin. The ancient Egyptians saw in their name for Philae an etymology with the meaning "island of the time [of Ra]", i.e. creation, but the island’s history is later than that.

What we refer to today as Philae is the main temple complex relocated from that island, after the High Dam was built, to the island of Agilika. It was the center of the cult of the goddess Isis and her connection with Osiris, Horus, and the Kingship, during the Ptolemaic period of Egyptian History.

Today, there are two dams at Aswan but of course, in ancient times, there were none. Prior to the dams, Philae Island occupied a position at the beginning or southern end of the First Nile Cataract, where the river gathered speed, dropping sixteen feet in swirling eddies and turbulent falls of white water for a distance of three miles. Various pharaohs attempted to calm or at least provide better passage around these rapids. Pepi I built at least one canal, as did Merenre, as early as the Old Kingdom, but later kings would also, such as  Senusret III.

There were numerous islands in the region, Amelia Edwards says hundreds, including Biggeh, the temple's current location of Agilika, a group of small islands at Awad and El Hasa, and below the Cataract (north), Siheil and Elephantine.

During early times, the priests of Philae claimed that the source of the Nile was bottomless and lay beneath the rocks of Biggeh, where half the river rose to flow north and half to flow south. Their rivals were the priests of Elephantine, who made the same claim. Indeed, the river around these islands was even then over one hundred feet deep in places, with confusing waters that could twist and turn in all directions.

This trek of water was hazardous in ancient times, a fact that escapes the modern visitor to Agilika Island. Amelia Edwards, the fearless Victorian Egyptologist saw it differently than we do today. She recounts:

"At Assuan, one bids good-bye to Egypt and enters Nubia through the gates of the Cataract - which is, in truth, no cataract, but a succession of rapids extending over two thirds of the distance between Elephantine and Philae. The Nile - diverted from its original course by some unrecorded catastrophe, the nature of which has given rise to much scientific conjecture - here spreads itself over a rocky basin bounded by sand-slopes on the one side, and by granite cliffs on the other. Studded with numberless islets, divided into numberless channels, foaming over sunken rocks, eddying among water-worn boulders, now shallow, now deep, now loitering, now hurrying, here sleeping in the ribbed hollow of a tiny sand-drift, there circling above the vortex of a hidden whirlpool, the river, whether looked upon from the deck of a dahabeeyah or the heights along the shore, is seen everywhere to be fighting its way through a labyrinth, the paths of which have never yet been mapped or sounded."

Of course, one can still get a glimpse of these cataracts north of the Old Aswan Dam. In ancient times, travelers made their devotions at Philae before continuing through the dangerous territory of the south to the "Land of Ghosts".

On the island of Sehel are more than 250 inscriptions from pilgrims and travelers coming to and going through the area, dating from the fourth dynasty down to the Ptolemaic period. Pepi I cut canals through the cataract to assist boat crews on their way to the calm water above Philae. Harkhuf passed through here on his way to Nubia during the reign of Pepi II. Also here on Sehel is the so-called Famine Stela, inscribed during Ptolemaic times but related to the reign of King Djoser in the 3rd Dynasty. It states that the king decreed that large tracts of land on both sides of the river stretching from Elephantine south should be given to Khnum’s temple, along with one-tenth of all produce and livestock raised as well as taxes on caravans and gold mining. There is an identical decree in the temple of Philae, carved at the base of the eastern tower of the second Great Pylon.

Such was the power of the gods, or at least the belief therein, that according to an inscription on the base of the eastern obelisk standing in front of the Great Pylon, during the reign of Ptolemy VIII, Euergetes II, and Cleopatra III his second wife, the priests complained that they were being forced to refund the expenses of civil and military authorities incurred during their stay at Philae. 

The priests were not being left enough resources with which to continue sacrifices and libations for the welfare of the royal family. Euergetes II released the priests from further payments.

The Island of Philae lied about four miles south of modern Elephantine, just to the other side of the Old Aswan Dam. It only measured about 500 yards from north to south and 160 yards from east to west, which meant that it was almost entirely covered with temples and other monuments. These were protected from the Nile Flood during ancient times by high walls, quays and terraces. In fact, before the building of the first dam, the Island always stayed clear of the river, safe on its granite foundation against the turbulent rush of the flood with its abrasive silt.

Prior to the building of the Aswan Dam, the engineer in charge, Captain Henry Lyon, was asked to underpin the monuments of Philae so that they could withstand the submersion, which he did. He also excavated part of the site where he discovered the remains of some Christian churches.

After the Old Dam was built, it created a lake extending south some 140 miles back to the Sudanese border. In fact, the height of the dam was at first restricted because of the protests made by people interested in preserving Philae and the other temples and monuments from submersion. Winston Churchill cared little for this. He remarked that:

"This offering of 1,500 millions of cubic feet of water to Hathor by the Wise Men of the West is the most cruel, the most wicked and the most senseless sacrifice ever offered on the altar of a false religion. The State must struggle and the people starve, in order that the professors may exult and the tourists find some place to scratch their names."

So the water level was raised, and the temples and structures on Philae were flooded each year from December to about March, and had to be visited during this time by boat, passing through the Kiosk of Trajan and into the court of the Temple of Isis.

All did not turn out as badly as thought, however. The water ended up saving the temples from erosion by sand storms and helped to remove salt deposits which were damaging to the stonework. Regular inspections of the site showed that it suffered less damage than might have been expected, save for the paintwork that was washed away by the new lake created by the Old English Dam.

Then, construction on the High Dam began and, as with a number of other monuments south of Aswan, the temple and other monuments had to either be moved or lost beneath the waters

In reality, Philae would not have been lost under the water of Lake Nasser itself, but rather the lake that was formed between the High Dam and the Old Dam. It was the only major monument located in this region. it would have been almost permanently submerged, but worse, this small lake is subject to a daily rise and fall of several yards, which would have inevitably eroded the temples completely.

This was accomplished during the 1970s, when the Philae monuments were moved to Agilkia northwest of Philae Island. Since waters already engulfed the monuments at Philae, a coffer dam had to be built around the island and then the water pumped out. This work began in 1972 and was finished in 1980 as a cooperative effort of UNESCO and the Egyptian Antiquity Organization. The new location was carefully landscaped to make it resemble Philae as much as possible. Some 40,000 blocks, weighing about 20,000 tons were moved to the new location.