From the Introduction:
On a small hill, carefully cleared of all vegetation, rise these low walls. They are the only remnants off a long fallen tower it seems. More stones strewn about other nearby hills suggest, that other ruins might still be awaiting their unearthing, biding their time protected by a layer of earth.
Someone made an effort to clear at least the space enclosed by the walls of rubble, unearthing a spiral staircase leading deeper into the earth. They even went as far as to reactivate some of the ancient glow stones in the tower ruin, giving it an eerie look at night.