Alien Erosion

''A facility this size could not have been excavated in the two or three years that the Chimera have occupied Bonn - that would be an impossible engineering feat, even for a species as technologically advanced as the Chimera. This place must have been here already, or at least part of it. What if the Chimera did not build it in the first place, but some other alien race? The excavation marks on the rock formations here under the bridge are all smooth and worn by dripping water, the result of a natural erosion processes that would have taken hundreds of thousands of years. Whoever built this facility, built it a long time ago. -- Journal Entry, 01 September, 1951 -- James Grayson''