- You may be looking for the space shuttle Atlantis.
Atlantis was an ancient civilisation located on the island of Thera.
An underwater Atlantean outpost survived beneath the ocean, off the Azores. In 1970, Professor Zaroff discovered the survivors and proposed to raise their settlement from the ocean floor. This would have destroyed the Earth. Zaroff died in the attempt due to the Second Doctor's intervention. (TV: The Underwater Menace)
Later, the Dæmon Azal pointed to the destruction of Atlantis as a warning as to what might happen if he considered Earth, a planet that the Dæmon had helped along, a failed experiment. (TV: The Dæmons)
Other locations of the same name
The Epoch created a world that was very similar to Atlantis. It was destroyed by Bernice Summerfield and Ruth. (AUDIO: The Kraken's Lament, The Temple of Questions, Private Enemy No. 1, Judgement Day)
Behind the scenes
Noting this, former Producer Barry Letts' noted in his introduction to the first edition of The Doctor Who Programme Guide that Atlantis had three different and incompatible explanations for its destruction. The line in Transit references this.