Ley line

Ley lines were cracks and bubbles of unimaginable levels of psi energy. They were one of the last surviving magicks of the universe that had not been cast out by the Gallifreyans when they became the Time Lords. This was because they were the least impossible sort of magic and the closest to actual science. A residue of psi energy formed a network of ley lines which stretched forth across the galaxy in improbable directions.

The Time Lords had long been aware of ley lines in times that predated the various Wars that they had fought. As they attempted to discard irrational magick in favour of rational science, a number of citizens objected; so the Time Lords turned the psi lines into weapons. One such waypoint of the ley lines was the planet Iphigenia that served as the basis for the Time Lords' Distant Early Warning line. This stretched through the galaxy and was studded with various receivers that were the size of mountains or small moons. Great parabolic dishes, disguised as craters, monitored the ley lines for eruptions of psi energy from beyond Gallifrey. (PROSE: So Vile a Sin)

Earth ley lines
According to one account, the ley lines and songlines of Earth were actually Euterpian beacons which were placed to mark out the sites which the planet should be cut open to release its energy to power Euterpian ships. However, with the destruction of the Euterpian mothership by a solar flare and the extinction of Euterpian civilisation, the Earth remained intact. (PROSE: Invasion of the Cat-People)

During World War II, Aleister Crowley advised the British team working on Project Big Ben that the failure of the German equivalent experiment, Project Chronos, may have been partly due to the machine's proximity to key lines. (PROSE: The Crawling Terror)

A ley line ran underneath an estate in High Wycombe. Some of the Eight Legs used it to travel there from Metebelis III. (PROSE: Return of the Spiders)

Kyra Skye, a human witch, was able to see/read the ley lines that were around San Francisco. (PROSE: Unnatural History)

In 2011, Gita Chandra wondered if all the light bulbs exploding in her house was caused by their being on a ley line. (TV: Sky)

In Wales, the House of the Dead was built on ley lines. (AUDIO: The House of the Dead)

A ley line ran through Sentinel Island. (HOMEVID:  Sentinel)

Equivalents to ley lines existed in other cultures, including the Australian songlines (PROSE: Invasion of the Cat-People) and the Chinese Dragon Paths. (PROSE: The Shadow of Weng-Chiang)

Highgate Cemetery was built on a ley line. (COMIC: The Highgate Horror)

A combination of ley lines and temporal anomalies made Greenford a target for cosmic phenomena. (PROSE: Not So Much a Programme, More a Way of Life)