Cruise along the cobblestoned streets of Florence, and you’re bound to bump into a trippai kiosk, where vendors preside over steaming pots of tripe boiling with vegetables and herbs. Order the classic lampredotto panino, and you’ll receive a crispy bun piled with tender slices of meat from a very particular part of the cow: its fourth stomach.

Lampredotto is likely the invention of working-class Italians who could afford only the less-popular parts of the cow, including the animal’s four stomachs. Known as the abomasum, the fourth stomach is covered in glandular tissue that likely made it the least desirable, and therefore least expensive, option along the digestive tract. Cleaned, slow-cooked, and sliced, however, it makes an affordable sandwich filling with a succulent, roast beef–like texture.

Most lampredotto sandwiches come drizzled with a parsley-and-garlic-based green sauce and chili-infused olive oil. The preferred panino presentation is bagnato, or “bathed,” in which the upper bun is dipped in tripe broth and perched warm and moist atop your lampredotto lunch. Sit along the river and watch the boats cruise by as you sink your teeth into a rich morsel of local heritage.