These are supposed “lines of energy” that connect some great monuments and important locations of the world. To be clear, it’s mythology – they’re not a scientific fact.
From How Stuff Works:
And maybe if ley lines were nothing more than that – imaginary lines that seemingly connect two important things – we would have an easier time simply accepting them. But at some point, some other interested parties hijacked the simple ideas and robustly embellished the story. Some claim that ley lines carry a powerful magnetic field, while others say they hold a psychic power. Still others are pretty darn sure that the lines are somehow associated with UFO landings – or that there are healing properties found in the “vortex” of ley lines
Why I Looked It Up
In the novel REAMDE, there’s an online RPG that uses teleportation between what they call “ley lines,” though it doesn’t seem that they’re connected to any monuments or anything.
Also, I remember an episode of The Librarians were ley lines were a plot point.