Dominican Priory in Dubrovnik: Founded in 1225, though the current Dominican church and monastery were built between the 14th and the 16th centuries. The monastery was constructed against the city wall to strengthen its north-eastern flank.
Jacob and I personally didn't find the gondola ride worth it. It was 80€ (!!!) for thirty minutes and the route we were taken on wasn't that great—we were on the canal for less than 3 minutes, which wasn't ideal. And there was a lot of gondola traffic during the time we went, which was around the early afternoon. It probably would have been better (more romantic) in the evening. Tip for @dmiloss.