Tapping the Big Iron Nut

Right beside the curb stood a real street giant: an old cast-iron fire hydrant painted bright canary yellow! I bounded across the rough asphalt cracks and leaped straight onto its rounded side nozzle. The cold metal had bumpy flakes of peeling paint, giving my boots great traction. I stretched up, reached around the dome top, and gave the big pentagonal brass valve nut a solid knock with my glove. Clink! A deep, ringing hum vibrated through the iron body straight down into the underground sidewalk pipes. There's serious water pressure sleeping under these street stones, and I gave it a proper test!