Discover the legends behind tiber island and basilica di san nicola in carcere on this 2 hour rome walking tour begin by exploring tiber island isola tiberina an ancient landmass in the tiber river that has an interesting and controversial history then visit nearby basilica di san nicola in carcere church of st nicholas in prison delve down to the churchs underground crypt to witness remnants of ancient rome still visible today this small group tour size is limited to 10 people ensuri