Built in the 1730s and set on a flat field surrounded by monks' quarters, Sanaienchi Gompa's main three-level prayer house has a real sense of age. Even if you can't find anyone with the key to let you in, there's a peephole in the front door through which you can spy on the central indigo Buddha figure, who's saucily straddled by a tantric damsel.
The monastery is 1.2km up a winding lane from Rinchenpong's bazaar, forking right at the only intermediate junction. If you have an hour or so to spare, don't miss walking on up to wonderful Resum Gompa.