Revelin Fortress is a real time commitment — fit it in only if it's a priority.
Allow 30–45 min (day).
By day a sturdy, lesser-visited fort with a good view terrace over the harbour and walls; by night its stone halls become Dubrovnik's main club. The honest catch is the daytime exhibit is thin and the real 'experience' is the nightlife, so it's two very different visits — come for the view and quiet, or come at midnight, not in between.