Sunomata Castle is a modern reconstruction tied to the story of Toyotomi Hideyoshi's rapid fort-building during the wars of the 16th century. The nickname "one-night castle" is more legend than literal fact, but the tale is part of how the place is remembered.
The museum inside is small, and the structure is not original. Go if you are following Sengoku-period history around Gifu and Sekigahara, or if you want a short side trip from central Ogaki.