A large iron sculpture by Chinese artist and activist Ai Weiwei that's designed to prompt thoughts about how different people and cultures come together has been acquired by Frederik Meijer Gardens & Sculpture Park in western Michigan, the organization announced Wednesday. Made of 99 iron pieces, the reddish sculpture called "Iron Tree" looks like a tree without leaves, but oversize stainless steel bolts that hold it together give it a mechanical, somewhat awkward appearance.