Sannai-Maruyama is one of Japan's most important Jomon archaeological sites, occupied for centuries from roughly 3900 to 2200 BC. Excavations found pit dwellings, long houses, storage pits, graves, pottery, lacquerware, and the remains of large wooden structures.
The reconstructions help because Jomon archaeology can otherwise feel abstract. Walk through the dwellings, then look at the artefacts in the museum and the site starts to make sense as a settled, organised community rather than a scattering of prehistoric objects.