The Large Ring at the 12:00 O'Clock position leads to the Stellar Platform of that node.
There are no Large Rings to 3:00 O'Clock or 9:00 O'Clock, indicating no lateral connections.
There are eight or more small rings at the usual positions small rings may be seen in the 3:00 and 9:00 O'Clock position.
These rings lead to sub-platforms. The sub-platforms are disks of approximately 1000 feet across that are covered with a geodesic dome and clear glass like panels.
The environment inside the sub-platform is identical to the environment on the main platform. The Sub-platform is on the surface of planets in the System of the Prime World. Whether the Sub-Platform is on Mercury in the direct sunlight, or on Titan being rained on by liquid methane the subplatform keeps the environment habitable.
The Sub-Platforms can open. When they do - Whatever mechanism that keeps the gravity, air and temperature the same as on the other platforms stops operating. The transition can be abrupt and destructive. When closed, in a matter of minutes, the habitable conditions return. How this is accomplished is unknown. Unbreathable air under crushing pressure at lead melting temperatures simmply melts away to the normal platform atmosphere at 65 degrees.
The materials that the sub-platforms, domes and panes are made of, like the rings and platforms resist all efforts at analysis. They blandly ignore all attempts to scrape, cut, bend or otherwise affect them.
See the GM's Notes for the special effects, if you're into that.
The Domes make wonderful staging areas for exploring otherwise impossible or difficult to reach places, but care must be taken.