Magic levels will normally flow naturally from areas of higher magic concentration to areas of lower concentration. The speed of the flow varies and can rarely be predicted to any great degree.
This flow is not affected by wind or gravity, a low area at the top of a mountain will refill at about the same speed as a low area in a valley.
Ley Lines are like rivers of magic that cut across the landscape and channel the flow of magic.
They normally originate in areas of higher magic and stop in areas of normal lower magic. Inside a ley line, the magic will be higher than the surrounding areas. Magic users can always sense the presence of a ley line and will be able to sense the direction of the flow.
Ley Lines almost always travel in nearly straight lines, ignoring intervening terrain or normal obstacles but they will tend to weave around otherwise high or very low magic areas.
Ley Lines will occasionally shift with some ebbing and flowing with the seasons.
Some of the largest fortresses are located at the end of a ley line.
Magic users need to be very careful when dealing with Ley Lines. The flow of magic in a line is not constant and can create unpredictable eddies of higher or lower magic. A magic user caught in an eddy of high magic could find their spells burning out, while a corresponding no magic eddy could drain all enchantments.
One of the main reasons Elves leave their cities is to follow and track the magic flow and to trace the ley lines.