Nice, Croatia has lots of nature to offer.
if you have the time and some ways of transportation, you should definitely check out omis canyon, itīs about 25 km down the coast. the islands should be pretty interesting as well, i have only been to the more northern ones. Spotwise, there are tons of them, Park Josipa Jurja Strossmayera just north of the diocletian palace is the meeting spot for locals.
have a good time.