Il Pulo (also Pulo di Altamura) is a huge hole in the ground, a  Doline or sink which was formed by the collapse of a cave beneath. Located in a vegetation-less plain, it looks like a meteor crater, similar to the Meteor Crater in Arizona. But it is definitely a much different way of formation. And with a close look this becomes clear: there are cliffs on the opposite side of the doline, obviously with karst caves and speleothems. To the west there is a sort of valley leading into the doline. It seems at some times of the year a small rivulet is flowing into the doline and vanished through the collapse debris into the cave below.

(Quote showcaves.com)