Umbul Sidomukti is a hillside pool and activity area above Bandungan, high enough to give broad views across the surrounding mountains. The pools are the main draw, but the site also has short adventure activities such as flying fox lines, valley rappelling, ATV rides, trekking, and horse riding.
It is most useful as a half-day stop if you are already exploring the Bandungan and Gedong Songo area. Go on a clear day; the view is a large part of the point.