Thames Museum is the town's main local-history museum, with displays on tangata whenua, James Cook's 1769 visit to the wider district, the gold rush, logging, shipping, and daily life in the old Thames settlements. It is not a glossy museum, but it is exactly the kind of place that helps the town make sense.
The modern Taonga Maori gallery is the best reason to start here before walking Grahamstown. After that, the photographs and domestic objects make the old shopfronts outside feel less like scenery and more like the remains of a town that once expected to be much larger than it became.