When Valmun gets close to the so-called wall, nothing jumps out at him. In fact, as he gets closer, he can tell that a great deal of whatever the structure is is actually half-buried in the sand. The wall looks like it was actually a great deal higher, but the sand seems to have risen higher than when it was built or the structure itself has sunk.
Beyond the pillars, walls, and other random outcroppings of black stone, though, there isn't anything that can be identified, nor do there seem to be any carvings on the stones. But once Valmun reaches the wall, which is about waist high, he notices a break in the trees. It looks like a path, though crudely cut, into the thick jungle, though the lack of sunlight penetrating the canopy of the trees makes it hard to tell if it goes any real distance inland.