Ston is a small town with the longest stone wall in Europe and the oldest active salt works in Europe, therefore called “town of salt”. It is located in an area where Pelješac peninsula is joined with the mainland. Throughout history, many rulers and dynasties ruled this area. Interestingly for this small town, Dubrovnik gained possession of Ston in 1333 and about 150 families from Dubrovnik moved to Ston. Architecturally and urban-wise, Dubrovnik was its model. The salt of Ston was an important import product of the Republic of Dubrovnik, bringing it quite a lot of profit. Ston remained part of the Republic of Dubrovnik until 1808, and then, after a short French occupation, became part of the Austro-Hungarian Empire until 1918. Ston and Mali Ston (Little Ston) are walled. Those walls were built during the 14th and 15th centuries and they total 5.5 km in length (originally, they were 7 km long). They have about 40 towers and 5 fortresses. The main purpose of the walls was to preserve the salt works and sea shell farms and protect the town. They are surely one of the more significant examples of the fortification architecture of that time. The walls were damaged multiple times in earthquakes. The renovation works lasted five years – from 2004 to 2009 – when they were opened for visitors. It takes about half an hour to tour the walls. 
Ever since the Roman times, the bay of Mali Ston has been known for its sea shell farming – oysters and mussels, and the Ston oyster has gained fame as an aphrodisiac.
You can visit St. Michael’s Church, Our Lady of Lužine’s Church, a 14th century’s fortress – Veliki Kaštio (renovated in 2013), the Republic of Dubrovnik office, the rector’s palace, Napoleon’s road. 
You can also go for a swim on a number of beaches nearby. 
About 4 km from Ston there is Prapratno bay where you can catch the ferry to Mljet (Sobra).