They're prevalent in man-made structures in art, design and architecture, both secular and sacred – such as the 9th-Century Great Mosque of Samarra or the Vatican Museum's spiral staircase.

VATICAN CITY --It’s one of the busiest ... As the sun rose, Crea let CBS News peek at Bramante’s spiral staircase. The doors were open and the museum ready. “No, absolutely not,” he ...

the staircase – also known as the Spiral Staircase – is the work of Giuseppe Momo. You can take the city train (Vatican City to Rome) to get to the museums, or hop on the Rome Metro.