The sixteenth-century building of the hospitable Holy Spirit, already in the medieval era the resting place for pilgrims traveling to Rome, houses in its spacious rooms the seat of the "G.Cortesi" Geological Museum. Known internationally for preserving the abundant fossil fauna of the layer type of"Piacenziano" (land of marine origin aged between 3.5 and 2.5 million years ago), the museum gathers today different collections that allow to follow the evolutionary history of the Po Valley basin, from when the area was completely occupied by the sea until the appearance of man. Among the finds include the molluscs local fossils (over a thousand exposed), but above all the magnificent remains of blue whales and dolphins discovered on the slopes calanchive that surround the ancient medieval village of Castell'Arquato. The central hall of the museum is entirely dedicated to the great remains of cetaceans in which stands out a rare fossil skull rorqual and several specimens of odontoceti. In the adjacent room is exposed a series of finds of the Po Valley basin Quaternary, between which a skull rhinoceros and some skeletal parts bear.