The dolina of Molfetta, known locally as the Pula, is situated at 2 km to the south-west of the town. Archaeological remains dating to the early and middle Neolithic periods were found in the bottom of this 30 m deep depression.

Archive research showed that the site was first occupied by the convent of the Sancta Santorum, built in 1536 and abandoned in 1575. The archaeological investigations, undertaken between 1997 and 2003 on the bottom of the dolina, brought to light an ossuary containing six adult individuals whose remains were disarticulated.

On the middle terrace and on the bottom of the Pula a vast workshop complex of Bourbon date was uncovered which can be identified as the “Regia Nitriera” (Royal Saltpeter Factory). This was constructed in 1784 following important mineralogical discoveries by the abbot A. Fortis (1741-1803) and canon G. M. Giovene (1753-1837). The Pula’s grottoes were rich in nitrates, in particular saltpetre, an essential component of explosive for guns and mines. The plant, only operative for a few decades, was closed due to its low productivity and described as already totally abandoned in 1808.

Of the industrial plant a monumental complex of tanks, channels, wells and cisterns were uncovered in which the leaching of the nitrous earth took place. This was extracted in great quantities from the grottoes situated on the northern side of the Pula. There were enormous circular heaps of earth and stones, with substantial diameters at the foot of this side of the Pula enclosed by dry-stone walls built at ascending heights. Also present were ramps of stairs for reaching the top.

On the middle terrace of the south side of the dolina stood the plant and warehouse of the “Reale Nitriera”. Linked to the rest of the production structures by a long pathway of limestone basoli for the ascent from the bottom of the dolina, they represented the final stages of the production cycle., The nitrous earth, which had previously been leached in the system of water tanks, was baked in the first building which had five furnaces. From the factory the saltpeter was transported to the next door warehouse where the nitrates were crystallized. This product took place in deep basins that were glazed internally and were manufactured locally in the 18th and 19th century.