The Sannai-Maruyama Site is one of Japan's largest early to middle Jomon Period sites. The site was designated as a Special Historic Site by the national government in November 2000. In July 2021, the "Jomon Monuments of Hokkaido and the Northeast" including the Sannai-Maruyama Site were registered as a World Heritage Site.

At the Jomon Jiyukan, excavated artifacts are displayed in the permanent exhibition room "SANMARU MUSEUM," a Jomon Theater shows films introducing the ruins, and a hands-on workshop allows visitors to experience making things (for details, see "Sannai-Maruyama Site Hands-on Workshop"). The Jomon Theater shows a video introducing the ruins.

Volunteer guides are also available to show visitors around the ruins.