For some reason, I thought that this structure (McGovern Weir, the photo is from flickr on uberzombie's photostream) traveled here from the 1904 St. Louis World's Fair, but I will acquiesce to more learned fans of the glass building. Anyone who has walked past the 5th Avenue florist outside of Green-Wood Cemetery's main entrance must have wondered about the dome of glass that houses the McGovern Florist shop. It's pretty darn cool.
Check out the handy explanation of its history on GowanusLounge. The text comes from Ruth Edebohls, the Coordinator of Urban Tours at the Center for the Urban Environment. She, in turn, acknowledges the work that Andrew Dolkart performed in his report to the Landmarks Preservation Commission in 1982.