I started reading a book on astrobiology last night (Life Everywhere: The Maverick Science of Astrobiology by David Darling). It looks like it is going to be mostly about extra-terrestrial bacteria rather than ET, but perhaps I should brush up on the spacecraft of alien civilizations. Here is a spaceship size comparison chart:
Here’s a closeup:
Grace and Peace
P.S. I had a similar post in 2006: Museum of science fictions spaceships.