The sites in the Nara basin are very informative about the spread of rice farming through the western part of the Japanese archipelago and about the associated transition from the Jomon to the Yayoi period of Japanese prehistory. The ridges were carefully planned to ensure that the water irrigated all the paddies. A number of large-scale excavations were recently undertaken in the southwestern Nara basin in advance of the Keinawa expressway linking Kyoto, Nara and Wakayama, which crosses the basin from north to south. The area affected by the construction of the new road had been paddy since at least medieval times and, unlike many of the more urbanized parts of the region. Excavations at Nakanishi-Akitsu began in 2009 and are continuing. Twenty seasons of excavations have taken place to date at Nakanishi, with early Yayoi paddies investigated between the fourteenth and twentieth excavation areas, in conjunction with the construction of the Keinawa expressway.