The Simon­et­ti Stair­case (also called Snail Stair­case or Momo stair­case) is the Vatican’s well-known and most pho­tographed set of stairs. Formed by two sep­a­rate wrought iron stairs – one going down and the oth­er going up, they twist togeth­er to form a dou­ble helix. This is designed to allow peo­ple descend­ing to not meet the ones ascend­ing. This ensures unin­ter­rupt­ed traf­fic in the Vat­i­can muse­um.