This is a very easy tutorial showing you them 3 wierd rings seen in Quake2

1. Create a fairly large room about 600x600x600 and place your info_player_start and some lights in there.

2. Now in the center of the room place an entity for the misc_blackhole

3. Compile your map and when you load it up you'll have a big room with 3 lasrge spinning rings in there :)

Download a sample map