Randezvous with Rama is one of the most amazing classic science fiction stories. An alien object enters the solar system and a groups of explorers are sent to investigate. The object is a rotating cylendar and with a large radius, thus sustaining 1 g gravity in the inside of the cylendar. As the group of exploreres enters the inner side of Rama, a deep frozen alien world wakes up.
As an addendum, there has been talks about making this into a movie. Morgan Freeman has the rights and supposed to have Fincher as director. It is now 10 years ago the project was initiated, so I highly doubt this movie will be finished. Maybe some day!!!