Two words: Mercato Testaccio.
If you're a foodie traveling to Rome, this is the place for you! Right next door to the building is the most incredible open air market with all the Italian delicacies you could dream of. We got breakfast and cappuccinos there every day, as well as stocking up for siesta snacks for after we came home from sightseeing. Casina Testaccio itself is also architecturally wonderful - a contemporary Italian studio apartment nestled within a building from the mid 19th century. Coming from the US, this juxtaposition feels incredibly fresh and provided the perfect place to relax and rest our feet at the end of the day. Will recommend to anyone I know who is traveling to Rome!