Enter A single race at Watkins Glenn and then start a practice session.
go out of the pits like you normally would but take a left and go
backwards just as you come out. At the beginning of the front stretch
turn around and go in the regular direction. just at the end of the
front stretch, there is a grass patch. Turn onto this patch at full
speed and you will fly into the air. If you have turned at the right
spot then you will fly over the fence and into a secret place. (just
make sure that when you hit on the other side that you brake or else you
will be brought back onto the track)