Not so many people take the ferry over to the island of Lokrum, but I really think it's worth it (even though, like everything in Dubrovink, the ferry is quite pricey). Lokrum is more quiet and peaceful than the old town and has beautiful views, a botanical garden, free roaming peacocks and interesting legends rank around the island that have to do with the assassination of Queen Sisi, but read for yourself: https://www.absolute-croatia.com/travel-magazine/legend-of-lokrum-island.