The Great Spacer
The Great Spacer is a gigantic "mother ship" used by the Plejaren, which only exists in outer space. Thus, it does not land on a planet, for it is it's own small man-made, self-contained world. It is of enormous size, about 17 kilometers (a little over 10.5 miles) tall, and has a crew of 143,000 human beings and androids. This technology was gained by the Plejaren from the Timmar, Asket's people, in 1971.
The Great Spacer is an egg-shaped ship, and is divided into roughly three sections. The bottom of the ship is the entrance/exit to a "parking lot" for thousands of beamships of the most diverse styles of construction to hover, and the maintenance area is also located in the bottom spheres attached to the outside. The middle section of The Great Spacer contains living quarters, recreation centers, gardens, parks, science laboratories, educational facilities, etc. The top sphere is 1 kilometer in diameter and houses the equipment to control the ship, where Billy first met Ptaah. Although the roof of this top sphere is made of a thick metal and is absolutely safe, it is equipped with a technology which projects the surrounding view of outer space for the occupants controlling the ship to see where they are in space. Therefore, it is as if they are working on a platform in space with nothing above their heads, with an unobstructed view of all of the surrounding stars, galaxies and nebulae.
The Great Spacer is also capable of making hyper-leaps to any place in space within a tiny fraction of a second. They simply enter in the coordinates to their desired destination, then the stars blur for a fraction of a second and they are transmitted to their new surrounding area in space.
Source: Message From The Pleiades Volume I (Contact Report 31), and Billy For Kids