It's about eight hours march across the dry desert to reach the dome, but it is easy to find. It glitters and glistens in the sun during the day so that it can be seen for many miles. It is also exactly the same as the dome that was dreamed about and drawn later.
Near the dome, there are obvious signs of a fight -- churned dirt, bits of dried blood, a broken spear, some torn robes, and so forth. The robes are clearly the same as the Aeon Priest robes you would have seen examples of within the tower.
You also notice that a large group (some on foot, some mounted) came to this spot from the east and moved westward.
A Perception check may reveal more information.