In the sense defined by Alfred Watkins in the 1920s, leylines are alignments of ancient sites observable in the landscape. According to Watkins, prominent features of the terrain—such as megaliths, burial mounds, churches, and fortresses—are arranged along straight lines to serve as visual markers. These alignments are thought to have facilitated navigation, trade, and the organization of territory since the Neolithic period. The original concept is grounded in strict geographical and cartographic observation, without reference to the energetic or telluric forces proposed in later interpretations.
Through their reliance on straight lines, landmarks, and large-scale spatial relationships, leylines fall within the field of archaeocartography, which examines the ancient structuring of territories. They also intersect with archaeoastronomy when certain alignments appear to incorporate solar or stellar orientations, suggesting an articulation between landscape, human movement, and celestial cycles.
The terms alignment or symplanicity will be used as appropriate when a connection to an ancient structuring of territory is difficult to establish. Finally, the term alignment is most appropriate when a linear sequence of disparate sites, lacking historical or symbolic continuity, results from pure mathematical chance.
