La Casa del Caffè Tazza d'Oro is a tiny, bustling espresso bar a short walk from the Pantheon where you should expect a queue and quick counter service; order a straight espresso or their famous coffee granita with whipped cream, pay at the counter (cards are accepted but having some cash can speed things up), and either drink standing at the bar like locals or buy beans/ground coffee to take home. Seating is very limited, peak times get crowded, and service is fast, so plan for a short, authentic coffee stop rather than a lingered meal.