But we now know that the ocean floor island was part of the castaways' purgatory. So did the island sink when they finally moved on? We'll never know.
Losties first got their glimpse of the giant four-toed statue watching over the island at the end of season two.
The statue in modern times is severed at the ankle, but flashbacks to the early Jacob days have included views of the back of the full statue. It appears to be an Egyptian god, the most popular theory that it's Sobek, a Nile god with the head of a crocodile.
It was revealed at the end of season five that Jacob lived inside the statue, but it was never revealed where it came from or why it watches over the island.
The show relied heavily on Walt -- Michael's young son who was being brought back to live with his father after years of estrangement. When they crashed on Oceanic 815, they crashed along with Vincent, Walt's loyal yellow Labrador retriever.
Walt was supposed to have been special, to be able to do things and see things the others couldn't, including teleporting while being held hostage by the Others. But then his father took him off the island, and we saw little of him after that.
Michael ended blowing up along with Widmore's freighter -- can we call being blown up pulling an Arzt? But Walt hasn't been seen since a brief meeting with John Locke in season five's "Life and Death of Jeremy Bentham."