Essa é provavelmente a série Great Ship de Robert Reed, cuja primeira entrada é o romance Medula .
When a jovian sized, artificially-created structure enters the galaxy, a society of technologically advanced humans (capable of interstellar flight and functionally immortal) are the first to intercept and investigate it. Finding it to be an intergalactic ship, they decide to convert it into a cruise ship, inviting alien races to join them in its massive, uncharted interior as it makes a slow circumnavigation of the Milky Way.