Rome's most revered espresso bar, open since 1938, located between Piazza Navona and the Pantheon. Famous for its gran caffè — espresso pre-sweetened and blended using a secret recipe — which is served to every customer unless you specifically request it without sugar (ask for amaro). The coffee is roasted on-site and the result is consistently excellent.
Standing room at the counter, as in any proper Roman bar. The queue moves fast. If you only have coffee once in Rome, have it here.