In the San Andeas map, there is a tank on an island by itself in South-East Woodside. There is no apparent way on to this island, except maybe by driving a bike off the edge of the bridge, and even then, no apparent way to get the tank off the island.
How can I get this tank? Is it involved in one of the missions, is it an extra side-game, or is it a kill frenzy, or just a teaser?
I am currently up to level Mandarin Madness (or something), the first level on the San Andreas map.