Gta San Andreas flying under the world

To do this trick you will need to know how to do the "get through solid objects" trick.

In Los santos (where there is a train tunnel heading towards Red County) walk up to stairs at the tunnel and you should see a building and some hills or mountains.

Now do the hydra trick into either the building or the mountains here. you should now be under the mountains, if so i suggest the jetpack cheat
( Left, Right, L1, L2, R1, R2, Up, Down, Left, Right(x2))

Now you can follow the path and fly under buildings, mountains roads and all other kinds of places.
note that it is not very easy to get back to land