The Saihōji No. 1 Kiln site (National Historical Site) at Kashiwara, Hōryū-machi in Suzu city is the only surviving medieval kiln with a ceiling attached. However, as an underground kiln it is a rare example, since Suzu kilns were generally built aboveground. This kiln may have been an attempt by potters at mass production by digging into the ground to create a large kiln, as they may have reached the limitation of kiln expansion above ground. Unfortunately, as the site was located where underground water sprung out, it appears that the potters were unable to obtain the required kiln temperature and consequently had to give up firing in the kiln at an early stage. From the style of mortars found at the site it can be concluded that this was likely the last kiln of Suzu Ware. The flames of Suzu Ware firing that had continued for around 400 years thus died out.