I can help.
Go right on Fortree.
When you get to the grass, walk through it and go accross the bridge
Then go south
And when you reach grass with paths going through, I advise you to go on your bike so you wont go in the grass
When you get to a wall, jump over it an go right until you get to another wall, jump over that too
Then go accross the bridge
And then go south until you get to berries
Go up the steps and through the grass
And then go up more steps and you will see a hiker and a cave with six rocks around it.
That is Ancient Tomb