Museu Sacaca is the city's best cultural museum, named for a local healer and organised around Amapá's riverine and forest traditions. Expect reconstructed houses, boats, medicinal-plant displays, and exhibits that make more sense of the state than a standard civic museum would.
It is especially useful if Macapá is your first stop in the far north. The museum gives context for the river communities and indigenous influences that shape daily life beyond the capital.