Gravett Island is an isolated and uninhabited island located in Earth's Pacific Ocean.
After having travelled back to 2063, the USS Enterprise-E was taken over by the Borg. Captain Jean-Luc Picard initiated the ship's auto-destruct and evacuated his crew to Gravett Island, in order to keep them out of history's way. ("Star Trek: First Contact")
It is interesting to note that although Picard asked his crew to land at Gravett Island, his orders were to go to "a quiet corner of North America." Perhaps was Gravett was used as a rallying point for the crew, but this is purely speculation.