The Bajoran Wormhole
A stable, artificially generated passageway to the gammaquadrant. The wormhole, which is located in the Denorios Belt in the bajoran star system, was created by the beings referred to by the Bajoran people as the Phrophets. The prophets live inside the wormhole.
The Q Continuum
This is the the place that all we Q's are occupying, living in. It is sort of a home to us. The problem is that it is so boring there. I have already done the scarecrow a thousand times. Once, I and another Q showed it to some humans. Actually, a human and a Vulcan. They saw a desert, with a road, a house, and a scarecrow. That is the only time any non-Q have ever seen the continuum.
The Genesis Planet
A class-M planet, created in 2285 when Khan detonated the Genesis device inside the Mutara nebula. The planet only existed for a couple of weeks, due to the use of protomatter in the genesis process. Unexplainably the planet gave life to Spock's dead body. The Genesis planets aging process was speeded up enormously, and was somehow connected to Spock.
The Guardian of Forever
The Guardian of forever is a time portale that can take you to any time that you could wish. It was created more than five billion years ago by a -- at this time -- dead civilization. The guardian can respond to questions; It is programmed to speak. But it will only answer questions about time, and something that it never speaks about is it's origin, except that it is it's own beginning and it's own end.
The Dimensional overlap in Tholian Space
A place in tholian space where several dimensional planes overlap. The overlaps disturbs senses and makes people go mad. It has been proven that you can transfer to another dimension and than return back alive. The starship USS defiant was lost there in 2268.