Inari has two things going on. The village itself, on the southern shore of the lake, is small — a single main street, a handful of buildings — but punches well above its weight thanks to the Siida museum and the Sajos Sámi cultural centre, which between them make it the unmissable place in Finland to learn about Sámi culture. Allow at least half a day for both.
The other half of the trip is the surrounding wilderness: Finland's third-largest lake right in front of you, two of the country's largest national parks (Lemmenjoki and Urho Kekkonen) within reach, the Pielpajärvi wilderness church an hour's walk through the forest, and the auroral skies overhead all winter. Inari is best treated as a base for several days of slow Arctic exploration.