Cianjur is a valley city in West Java, sitting between Bandung, Sukabumi, and the Puncak pass. It is not polished, but it gives you a slower Sundanese stop on the old Jakarta-Bandung road, with rice fields close to town and mountains rising beyond the edge of the city.
The main reason to come is Gunung Padang, a terraced megalithic site in the hills south of Cianjur. The city also works for a local hike up Mount Mananggel, where the reward is less a single monument than the walk through paddies and villages.
Stay practical about it: Cianjur is a good one-day detour if you are already crossing West Java, not a substitute for Bandung or Yogyakarta. The small local pleasure is breakfast - Cianjur-style bubur ayam, a chicken rice porridge that locals take seriously.