Meeresaquarium Nautiland is a family-oriented aquarium in Sonneberg, useful on a wet day or when children have reached their limit with historic toys. It is not the reason to travel across Germany, but it broadens the town's small menu of indoor attractions.
Treat it as a practical add-on rather than a cultural highlight. Paired with the German Toy Museum, it can make Sonneberg work surprisingly well for a family day out.