Originally it was located on the Island of Philae. This temple was dedicated to the goddess Isis and its construction started during the III ac century. Isis is an important figure in the ancient world. She was related to the funeral rites and she was considered a "giver of life", a healer and protector of kings. The temple was moved and reconstructed in the small island of Agilkia, before it was submerged completely under the Asuan Dam waters. It was nearly lost under water when the second part of the Asuan dam was built, but with a joint between the UNESCO and the Egyptian government it was saved and protected. So this temple are now part of the open museum of Nubia and Asuan, declared by the UNESCO as a World Heritage Site in 1979.
The Templar complex is composed by several buildings, sucha as "the hall of Nectanebo I (380-362 a.C.), the "Temple of Arensnufis",  the Mandulis Chapel, the galley of Ptolomeo II Filadelfo, two obliscs, The temple of Isis and the Hat-Hor temple.
The temple of Isis one of the most beautifuls. It has antiques decoratives scenes from the Ptolomeo II Fildelfo kingdom. The hall  of Nectanebo is also important because is the oldest conserved building, and its the entrance from south to north to the Outer court and the other buildings. 
This is a gorgeus place to visit outside Cairo. A journey with lots of fun and culture.