Ley lines are alleged alignments of a number of places of geographical interest, such as ancient monuments and megaliths, that are thought by certain adherents to dowsing and "New Age" beliefs to have spiritual power. Their existence was suggested in 1921 by the amateur archaeologist Alfred Watkins, in his book The Old Straight Track. The believers in ley lines think that the lines and their intersection points resonate a special psychic or mystical energy. However, they never suceeded in providing an objective proof for the existance of ley lines which would convinve scientists, or to make the alleged energy availalbe for practical purposes. The concept of ley lines remains, therefore, classed as a "pseudoscience".
The discovery of Ley lines and the development of the ability to systematically chart them and make use of them was a central aspect of the Thaumaturgical Revolution, distinguishing modern magic from that of the Kaunian Empire when mages were only aware of a few, widely dispersed spots where magical energy could be tapped, and did not know of the lines connecting these spots.
Utilization of ley lines had two major aspect - as a source of plentiful energy which could be used for a variety of daily life purposes, and as a means of quick and reliable travel by ley line caravans speeding over the countryside, deriving their energy from the ley line itself (but, by definition, restricted to moving along the ley line's route).
Ley lines had a decisive impact over the pattern of human habitation, and determined the economic position of cities and whole countries. Cities which were located on or near a ley line (and even more so - at the intersection of two or more ley lines) tended to develop and grow fast. Those far from a ley line, which continued to be dependant on slower and less certain means of transportation, were doomed to stagnate, shrink or disappear altogether.
Setuval, the capital of Lagoas, was considered to be at the intersection of more ley lines than any other city in the world - which considerably influenced Lagoas' attaining the position of a major commercial power. Conversely, Unkerlant's economic backwardness was in part attributed to having few ley lines in its vast territory, and having many areas where peasant villages were isolated and cut off due to having no ley line anywhere near (for example, the native village of Garivald). It was not clear, however, if this was due to the objective dearth of ley line in Unkerlant, or to the Unkerlanters' faulure to locate and make use of all the lines which were there.
Ley lines had also a key role in times of war. An invading army sought to get contol of ley lines, as the quickest way of penetrating deep into enemy territory. A retreating army resorted to magically "overloading" and sabotaging the ley lines, making them unusable until the invaders' mages repaired the damage.
During the Derlavaian War, Algarve made a sinister use of the ley lines in order to transport horribly crowded Kaunian prisoners to the "Victory Camps" where they were killed and the their life energy used in war.
Ley lines also revolutionised human activity on the sea. Ley line ships replaced the older sailing ships in both commerce and war. Modern naval stategy concentrated on defending the ley lines leading to a country or used by its commerce, or attacking and taking over the enemy's ley lines. In both peace and war, the rest of the world's seas, where ley lines did not pass, was largely abandoned, except for pleasure yachts.
This turned out to be a disastrous oversight for Sibiu, an island nation and vetran maritime power, whose admirals neglected to guard against an attack launced by old-fashioned sailing boats bypassing the ley lines - which Algarve launched, pressing yachtsmen into service.