That's the now famous globe-like sculpture named "The Sphere"* that was crumpled by debris when the Twin Towers collapsed on 9/11/2001.

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* Located at WTC courtyard named the Austin J. Tobin Plaza http://www.pbase.com/carinoza/image/138033448 ),
the famous 1971 "The Sphere" sculpture is made by German sculptor Fritz Koenig.

Despite its proximity to the Twin Towers, it remained structurally intact despite the visible dents and holes
caused by the debris from the airliners that crashed into the buildings and from the collapsing skyscrapers themselves.

Six months after the attacks, it was relocated to Battery Park on a temporary basis —without any repairs— and formally rededicated with
an eternal flame as a memorial to the victims of 9/11. This unlikely 'survivor' from that infamous day has since become a major tourist attraction.