[@Rapid Reader]
Clara cannot see the harpoon shooting contraption, however she can see that very high above them, there appears to be another landmass. Given the ramp like curvature of the land, it could be inferred that the strip of land they're on does somehow loop upward, resulting in there being land above them.

There also appear to be several outlines on the land which indicate either large boulders, mountains, structures, or creatures, but it's too far away to tell clearly.