From the 7th to 8th centuries, straight roads and grid-like city blocks aligned with the cardinal directions were constructed in the Nara Basin. This study examines the surveying techniques that may have been employed in their layout. One method likely involved observing circumpolar stars, particularly the simultaneous transit of two stars with nearly identical right ascensions. Another method utilized the directional lines of sunrise or sunset, whose azimuths remain stable for several days around the summer and winter solstices. These orientations were recorded in relation to prominent mountains and saddle-shaped features on the skyline.
