Again, notice the difference in the size of the building on the right and the tent.
OK, give up? Turns out that inside is the Temple of Apollo Epicurius. The tent protects the temple from further deterioration. It is under a section-by-section restoration process right now.
For some reason, this 5th century BC temple is located on a remote mountaintop. It's a striking location, but how in the world did pilgrims make their way there, way back when? It's not near any known ancient settlements. Maybe only the truly dedicated (and strong-legged) made their way to this temple to the god of healing.
