Ley lines are the term used for the straight tracks that connect through geographical and historical places in the UK like Stonehenge. Several researchers from the 18th century onwards noted that ancient sites were built along them but, it was the amateur archaeologist Alfred Watkins who first used the term Ley Line in his books Early British Trackways and The Old Straight Track. He theorised that the trackways were created by people travelling overland by link of sight navigation during neolithic times.
After Watkins died in 1935, others theorised that Ley lines may be orientated to sunrise and sunset during soltisces, lines of cosmic force, spirit lines, roads of the dead or magnetic nodes which connected important sites or are elements of a shamanic landscape. These theories have been criticised, but, in some ancient cultures, appear to have similarities with Fung Shui and has produced interesting research into their magnetic and metaphysical meaning.
These straight roads have been discovered in many other countries including Peru and the USA, where archeologists found evidence of engineered roads built by the Hopwell, Miwok Indians,the lost Anasazi and the Maya. NASA aerial surveys have discovered paths which run through the mountain rainforest of Costa Rica, subsequently dated to AD500-1200.
In many societies, these lines are associated with the dead and the spirit flight of Shamans, whose out of body journey may have been induced by native hallucinogens. If you travel across or along a Ley line, you may feel the positive vibration that they emit, perhaps this may be why sacred sites, effigy mounds and geoglyphs have been created near them, or close to their convergent crossroads. Next time you go Ley hunting, try using dowsing rods to detect them in your area!
References:
http://pauldevereux.co.uk
http://en.wikipedia.org/wiki/Ley_line