The Gasholder House, Troy NY:
People today somewhat vaguely remember that, in between oil lamps and electric lights, we used to light our homes and business with gas lamps. The gas was refined coal gas and, like all such volatile products, had to be stored carefully for distribution. The Gasholder House is a large gas tank, with a brick exterior wall and trussed dome, and supplied gas to Troy. This was, for its era of construction, fancy stuff...and today requires a paragraph of explanation.
One minor linguistic hangover: we call natural gas "natural gas" to distinguish it from the previously used "artificial gas."