Admire romes underground treasures on a 3 hour small group walking tour after exploring the ancient cattle market of foro boario youll discover temple ruins millennia old bridges and the streets of trastevere its in this neighborhood that the real gems await head underground at the church of santa cecilia and the basilica of san crisogono to discover a basement crypt and the remains of an ancient frescoed church numbers are limited to just 13 people