Start your trip with a visit to Diocletian's Palace, a UNESCO World Heritage Site that was built in the 4th century as a military fortress and palace for the Roman Emperor Diocletian. This impressive complex is one of the most well-preserved Roman monuments in the world, featuring ancient temples, columns, courtyards, and an underground network of tunnels and vaults. Walk through the busy streets of the palace and admire the ruins and architecture all around you. Don't miss the Peristil square, the Vestibule, and the Cathedral of St. Domnius, which is actually a mausoleum built by Diocletian himself.
Escape the city center and head up to Marjan Hill, a nature preserve and park that offers breath-taking views of the Adriatic sea and the surrounding islands. You can hike or bike up to the top of the hill, stopping at various lookout points and attractions such as the Jewish cemetery, the Church of St. Nicholas, and the Vidilica cafe. If you prefer a more leisurely stroll, take the road that goes around the hill and enjoy the pine forests and beaches along the way. Finish your day with a swim at Kasjuni beach or a sunset drink at Bene beach.
Wrap up your stay in Split with a morning visit to the Green Market, a vibrant and bustling marketplace that sells fresh produce, fish, cheese, honey, olive oil, and other local delicacies. Chat with the friendly vendors and sample some of the goodies, such as the aromatic lavender, the tangy mandarins, or the salty sardines. From there, take a leisurely stroll down the Riva Promenade, a seaside boardwalk that is lined with cafes, bars, and ice cream shops. Soak up the views of the harbor, the boats, and the palm trees, and watch the locals and tourists go by. If you have time and energy, stop by the Archaeological Museum or the Ivan Mestrovic Gallery.
If you have more time, consider taking a day trip to the nearby islands of Brac, Hvar, or Vis, or visiting the Krka National Park, which has stunning waterfalls and hiking trails. If you have less time, you can skip some of the attractions in the itinerary or combine them into one day (for example, you can visit Marjan Hill in the afternoon and watch the sunset from Vidilica). Be aware that some places, such as museums, may be closed on Mondays or public holidays, so check their websites or ask locals for recommendations. Finally, be prepared for crowds and heat in the summer months, and don't forget to wear sunscreen and comfortable shoes.