Morcilla is a type of Spanish blood sausage made with pork blood, rice, and various spices. It has a rich and savory flavor, with a slightly earthy taste. Morcilla is often grilled or pan-fried and can be enjoyed on its own or as part of a tapas dish. In El Retiro Park, you may find vendors offering morcilla sandwiches or tapas, allowing you to savor this unique and flavorful meat option.