An incredible cave territory, the Pulo sinkhole opens up at about 2km from Molfetta as a wide karst chasm carved through limestone, coming after the downfall of the ceilings of a number of subsurface caves.
As an outcome of the earthquake in Irpinia on November 23, 1980, it was declared dangerous and unfit for use and was subsequently closed to the public. 15 years later, recovery works started at the sinkhole, and it was subsequently opened to the public .
The location of the sinkhole was occupied since the Neolithic, as supported by the numerous archaeological discoveries and prehistoric grottoes whose corridors open up along the walls of the sinkhole, as with the caves Ferdinando and Carolina and the cave of the pillar. The ancient caves, both natural and partially man-made, located at Pulo di Molfetta and exploited in the Bourbonic period (18th and 19th century) for extracting saltpetre, used for the manufacture of gunpowder, were named after Ferdinand IV of Bourbon, king of Naples, and his wife Maria Carolina, who visited this site in 1790.
In the 16th century, the Capuchin Frias erected a small monastery on the sinkhole's western perimeter overseeing the area, which, in present times, symbolizes not just a location for reflection but also a special fort for studying Pulo’s unique natural phenomena.
In 1783, nitrate was discovered in Pulo Di Molfetta by Giuseppe Maria Giovene, a naturalist who shared his analysis with a fellow naturalist, Alberto Fortis.
Due to its holes abundance in nitrates, an innate element of gunpowder, in the succeeding half of the 18th century, the Pulo became the hub of economic and scientific attraction of the Kingdom of Naples and the House of Bourbon, which constructed the precious nitrary, a unique representation of industrial archaeology.
Overall, the Pulo of Molfetta is distinct from the others because it is a sinkhole in the well due to the sheer cliffs on the entire boundary and also a slumped sinkhole in relation to the proof that it originated from the collapse of the ceiling or a single large underground cave or, more likely, more tunnels and caves that are part of most karst adjacent wells (called polje), with collapses that have taken place stretch in time.
All the caves do not have calcium carbonate concretions because of the absence of dripping water. At the bottom of the Dolina are the remains of the Bourbonic factory, where saltpeter was concentrated and refined. The walls of Pulo are studded with several caves, which are improved even on various phases (up to four as in the "Cave of the Pillar") and often interconnecting underground passages denoting the intense karst activity.