Excerpts from Books and Wikipedia
"To avoid losing his grave goods, Tuthmosis I planned a new, secret burial place: a cave with painted walls, just as ornate as the inside of any pyramid, but with a hidden entrance. The valley where his cave was located later became known as the Valley of the Kings. . . . Tuthmosis I was likely the first pharaoh to use the Valley of the Kings, but because his mummy itself hasn't been identified (and his name appears on two different Valley sarcophagi), some scholars believe he was buried elsewhere." [Bauer: Ancient World, p. 207]