Above the present-day pier in Petrovac, the Venetians built a fortress in the 16th century, and the whole place was named KastelLastva after the fortress, which was called Kastio by the locals. The fortress was home to a permanent Venetian garrison. It contained stores for wine and other products that were exported by ships. Next to the fortress, the Venetians built the Lazaret, an infirmary which was mainly used as a place of quarantine, for the accommodation of patients during epidemics. Only the walls of these buildings have remained.
The fortress and the Lazaret are part of the recognizable landscape of Petrovac, framing the Bay of Petrovac and separating it from the Tuljanova Cave. After the construction of the pier, restaurants, cafes and a discotheque have been established in the last few decades, and this formerly deserted site has beenbrought back to life.