The entrance fee to visit the exhibition inside the citadelle is really low, so no reason not to buy a ticket to see this interesting historical structure from the inside. The exhibition showed art work of different artists, not all were my taste, but I really enjoyed the aerial photographs.
Citadelle Saint Florent, Via A Citadella, Saint Florent, Corsica, France
Visited July 2016. You can find my review about Citadelle Saint Florent also on TripAdvisor.