The Voitheia is a geodesic dome. The outermost layer of the dome was made of triangular glass panels that have a special coating to reflect all ultraviolet radiation from the Sun. The glass was manufactured to be over half a kilometer thick which now helps to keep all the heat in the dome. The glass is impenetrable and is strong enough to withstand the occasional collisions with meteors.
The Voitheia is the new and improved version of the Biosphere 2 (see image below).
It is significantly bigger and definitely had more success than the Biosphere. This particular building was made such that several other domes within it, you could think of it like an onion, layer after layer, or a Matryoshka doll. Each layer either holds a facility or residences for those of different social status. Below is an image of what one of the inner domes may look like, particularly the safari/zoo area, where natural habitats were recreated. (Imagine a rainforest shrunk in size and placed under a dome, like a terrarium).