Complex sentence: Unterwalden is the old name a forest-canton of the Old Swiss Confederacy, now organized as two half-cantons in central Switzerland, south of Lake Lucerne, an upper part, Obwalden, and a lower part, Nidwalden.
Split into simpler sentences: Unterwalden is the old name for what is now two cantons in central Switzerland, south of Lake Lucerne. It consists of two half-cantons, an upper part, Obwalden, and a lower part, Nidwalden.