»In which we fight fires

The New York Times has a nice piece explaining the purpose of the Siamese outside many buildings in Manhattan: the standpipe system. "At many buildings, parts of the Siamese and the plates covering the opening where it goes through the facade are brass, and it appears to be a point of pride among building managers or maintenance workers to keep that brass polished to a high shine."
More photographs of and the law concerning standpipes.