Ley Lines

Description
The world is crisscrossed with ley lines, the ancient foundations on which the world stood. These are loci of magic, and support the weave of magic. If a ley line is severed, a superhuman feat in itself, the area around the site would be cut off from the weave of magic; no spells will work, magic items lose their properties.

Function
At ley line confluences, magic is heightened. The physical landscape changes, and planar divisions are weakened. The Feywild may leak into the material plane, leading to a large influx of vegetation and Fey creatures. The same could happen for any other plane. Many wizards and magic users decide to build their towers and sanctums on these places.