Alexander Calder's wire sculptures are some of my favorite art works. I like the way they make the viewer think about material and line in three dimensions. They almost appear to be three dimensional line drawings standing free  on their own in space rather than remaining trapped within the page. They look to balance precariously, but Calder was a master with mobiles and sculpture was well aware of how weight would need to be distributed. I'm sure that these works are very sturdy in reality.