The steaming sewer gates in New York streets always seem so romantic in winter movies, but let me tell you—they’re anything but. Especially when the wind shifts and blows that steam directly at you, carrying with it the unmistakable scent of the city’s underground.

I’ve never experienced this quite so much in any other city, and there’s a reason for that. New York’s steam system is one of the largest in the world, powered by an intricate network of pipes that snake below the city. While the steam is largely used to heat and power buildings, it escapes through manholes for safety, blending with the less pleasant odors of the sewer system.

The steam, combined with the city’s unique aroma, is hard to escape—especially in winter, when it’s amplified by the cold air and those famous gusts of wind. It’s just one of those quirks of living in the Big Apple.