Image of the Day #9
(http://bruce.org.uk/images/spaceprog.jpg)
Here is a vector illustration providing the perspective in terms of the sizes of the crew modules used in Mercury (single crew bottom right), Gemini (two crew middle right) and Apollo (three man crew) manned rocket flight programs.
Long duration flight began with Gemina. The crew were cramped and you can imagine what a foul atmosphere it became over a 9-11 day mission. Apollo conditions were five star luxury by comparison.
You get a true perspective also of the size of the Saturn V rocket used in all the moon landing missions.