International Market Square building stairwell in Minneapolis, Minnesota. Largest commercial double helix staircase in the US - built with straight runs and flat landings it intertwines two separate sets of stairs, one for going up and one for going down. Formerly world headquarters and plant for Munsingwear company.
<a href="//commons.wikimedia.org/w/index.php?title=User:Ljn1111&amp;action=edit&amp;redlink=1" class="new" title="User:Ljn1111 (page does not exist)">Ljn1111</a>
<span class="int-own-work" lang="en">Own work</span>