Technologically, the Anu have been very advanced for millions of years. Their equipment is made to last the ages, and runs very efficiently.
The ship in which the Anu came to Earth was made for long-distance space travel. It was completely self-sufficient., and did not require any outside resources to operate. It was not very large, but as it was meant to sustain a mission of a lifetime, it had plenty of space for its crew to live and work.
As a research vessel, it contained many well-equipped labs and large areas in which biomes could be set up. Re-creating ecosystems within their ship from samples was a convenient way to study life on the planet below.
In our mythologies, we know this ship as “Nibiru”, ni-biru, which means something like “foreign home” or “temporary home”. Orbiting around Earth, it was the place where most of the Anu lived, for most of the time they were here.