Pathar ki Masjid is a small but significant Mughal-era mosque near the Ganges in old Patna. Its name means "stone mosque", and the building's restrained stonework gives it a different character from the larger painted and plastered religious sites elsewhere in the city.
Visit it as part of a broader exploration of Patna's riverfront and old quarters. The mosque is still a religious place, so dress and behave accordingly. Its value is historical and architectural rather than spectacular, but it helps fill in Patna's long Islamic chapter.