Split is a modern city and about a two hour drive north of Dubrovnik. The Ruins of Diocletian's Palace are massive and essentially create a historical downtown that is full of incredible shops, winding alleys, and food excursions. The city itself can be explored in a day, and is generally used as a jumping off point to get to nearby islands. If we had to do the trip again, I would recommend skipping Split, or just stopping by for an evening of food and exploring the downtown. It would have been more enjoyable to just go to a nearby island, and spend a few days relaxing.
The food scene is the best part of Split. We enjoyed bouncing around from bar to bar and finding different spots to sit outside and people watch. Most of the restaurants have seats in the streets, so an incredible ambiance is created.
On our only day spent in Split, we booked a food tour through airbnb. This was a private tour with an incredible local who was able to teach us not only about the food scene in the city, but also about the culture, history, and current state of affairs. During the tour, we went to the Split fish market to pick out fresh food and meet some of the vendors. We then picked up fresh produce and sheep's stomach cheese. After selecting our veggies, we took everything to Diocletian Wine House for preparation and lunch!
My favorite part of split was Kasjuni Beach and I wish we had gone here for a full day and not just an afternoon. The beach itself is stunning, and there is a great bar for food and drink. They have stand up paddle board rentals and kayaks as well. Explore the park and you will be able to find cliff jumping and deep water soloing. I came upon a few climbers who were free soloing on the cliffs, but unfortunately I didn't have the time nor shoes to join.