Beneath the modern buildings of Osaka lies a hidden world. This is the Sunaiseki Ruins, also known as the Yonchodan Ruins. It’s more commonly referred to as the Jomon Period Sunaiseki Ruins. They offer a glimpse into Osaka’s ancient past.
The Jomon Period Sunaiseki Ruins weren’t always a schoolyard. They were discovered during an archaeological survey in 1983. Construction was planned for the new Yochodan Boy’s School on the site. The initial survey unearthed a treasure trove of artifacts. These ranged from the Yayoi to the Kofun periods. Further digging revealed even older treasures from the Jomon period. This included remnants of a settlement. The discovery was so significant that it prompted a full-scale excavation. The school grounds became known as the Jomon Period Sunaiseki Ruins.
The oldest artifacts at the Sunaiseki Ruins date back an astounding 4,500 years. This places them in the Middle Jomon period. A particular type of pottery called Funamoto-style pottery was found here. It’s characterized by its coarse rope-patterned decorations and unique thumb-pressed markings. Some pieces even feature cord impressions along the rim. This pottery style is typically associated with western Japan. The discovery of Funamoto pottery at Sunaiseki, alongside pottery from eastern Japan, reveals the interconnectedness of these regions.
The Middle Jomon period was a time of significant change in Osaka. The sea had receded, creating a vast inland bay. This bay extended from present-day Osaka Castle to Higashiosaka and Yatsushiro. It’s known as the “Kawa-uchi Bay”. While the bay was at its largest during the Early Jomon period, it remained a prominent feature during the Middle Jomon period. The Sunaiseki Ruins were located only about a kilometer from the shoreline of this ancient bay. The dig revealed the ground level from the Middle Jomon period. It was about 6.8 meters below the current ground level of the school. This indicates the dramatic changes in the landscape over time.
The excavation also uncovered evidence of daily life in the Jomon period. A set of stone tools was discovered on the site of the present-day gymnasium. These included a stone axe and grinding stones. They were found arranged on the ground, suggesting they were left in place during use. Two and four grinding stones were discovered in separate sets, possibly from different households or activities.
The Sunaiseki Ruins also reveal insights into burial practices. Six deep jars, or dokan, containing human remains were found. These jars, dating to the Late Jomon period, served as burial urns. Some contained the bones of infants, while others held the re-interred bones of adults. This suggests a complex relationship with death and remembrance. Additionally, bone fragments were discovered in earthen pits. These were likely doko-ubo, simple earth graves.
While the site served primarily as a burial ground during the Late Jomon period, the presence of everyday tools and pottery suggests the presence of a settlement as well. The Sunaiseki Ruins offer a unique perspective on the Jomon people of Osaka. They show us how they lived, worked, and honored their dead. They serve as a reminder of the rich history hidden beneath our feet.