The Sultan's Palace is the most distinctive traditional landmark in Maradi, set on a broad plaza on the west side of the city. It is not a museum attraction in the usual sense but the seat of a living local authority, so the compound matters culturally as much as architecturally.
Visitors should be careful with expectations. You may only see the palace from outside, and if you hope for an audience or a closer look you need help from someone who understands Hausa court etiquette. Dress conservatively, ask before taking photos, and be patient; the waiting is part of the institution.