Palmer Mansion
...that the once-standing Palmer Mansion in Chicago, Illinois, had a self-supported spiral staircase which rose 80 feet into a tower?
...that the once-standing <b id="mwErY"><a href="./Palmer_Mansion" id="mwErc" rel="mw:WikiLink" title="Palmer Mansion">Palmer Mansion</a></b> in <a href="./Chicago" id="mwErg" rel="mw:WikiLink" title="Chicago">Chicago</a>, <a href="./Illinois" id="mwErk" rel="mw:WikiLink" title="Illinois">Illinois</a>, had a self-supported spiral staircase which rose 80 <a class="mw-redirect" href="./Foot_(unit_of_measurement)" id="mwEro" rel="mw:WikiLink" title="Foot (unit of measurement)">feet</a> into a tower?