This is a traditional cooking vessel in Vis, a small island in the middle of the Adriatic, about two hours' ferry ride from Split, Croatia. The method is called "pod pekom," which means that it's slow-cooked with embers on top and underneath.
Inside this vessel in particular was a lunch of monkfish, potatoes, rice, and some vegetables. We waited a good, lazy hour for the monkfish to be ready as we drank local wine and snacked on cheese and charcuterie.
Over four days we sampled many of the restaurants on the island, which are mostly homes that operate as agritourismos during the summer months. We were there in June, early enough in the summer that we had the place largely to ourselves. Finding a place for lunch after one beach and before the next beach meant driving through the vineyards and looking for hand-painted signs signifying homecooked food.