Humans have been throwing structures across water for thousands of years, and the stories collected along the way beat the engineering. Fifteen questions — cover the answers, lock in each guess, and keep score.

In May 1884, P.T. Barnum marched 21 elephants across the Brooklyn Bridge. Why?

To prove it was safe — a deadly stampede panic in 1883 had shaken public trust, and Barnum's parade, with the famous Jumbo along, calmed nerves and made headlines at once.

Who ran the completion of the Brooklyn Bridge for over a decade when its chief engineer fell ill?

Emily Warren Roebling — she mastered the engineering, managed the project for her ailing husband, and crossed first by carriage, reportedly with a rooster along for luck.

What happened to the 1830s London Bridge when the city replaced it?

An American entrepreneur bought it in 1968 for about $2.5 million and rebuilt it in Lake Havasu City, Arizona — and no, he always denied thinking he'd bought Tower Bridge.

What color is the Golden Gate Bridge, officially?

International orange — the Navy had lobbied for black with yellow stripes so ships could spot it in fog.

Is the Golden Gate really repainted end to end every year?

No — that's a myth. Crews touch it up continuously, a maintenance job that never actually finishes.

Why are the tops of the Verrazzano-Narrows Bridge towers farther apart than their bases?

The curvature of the Earth — the 693-foot towers stand so far apart that the planet bends between them, adding roughly 1.6 inches at the top.

What earned the Tacoma Narrows Bridge the nickname Galloping Gertie?

Its deck rippled in wind from day one — four months after opening in 1940, it tore itself apart in a roughly 40 mph wind; the only casualty was a cocker spaniel named Tubby.

What is the longest bridge in the world?

China's Danyang–Kunshan Grand Bridge — a high-speed rail viaduct running about 102 miles.

What is the tallest bridge ever built?

The Millau Viaduct in France — its tallest mast rises 1,125 feet, higher than the Eiffel Tower.

Why do soldiers break step when crossing bridges?

Marching in rhythm was blamed for collapsing England's Broughton Suspension Bridge in 1831 — and the order to break step has stood ever since.

Which is the only bridge in Florence the retreating German army didn't destroy in 1944?

The Ponte Vecchio — still lined with the goldsmiths' shops that replaced its smellier butchers back in 1593.

Where was the world's first bridge made of iron erected?

Shropshire, England, in 1779 — the aptly named Iron Bridge, its cast pieces fitted together like giant carpentry.

What does the Sydney Harbour Bridge do on a hot day?

It grows — the steel arch expands and can rise several inches, which the locals of 'the Coathanger' take completely in stride.

Why do bridges ice over before the roads leading to them?

Cold air hits them from above and below — with no ground beneath to lend stored warmth, the deck freezes first.

Which London bridge is the famous one with the towers?

Tower Bridge — London Bridge is the plain one just upstream, a mix-up that powers a thousand disappointed photographs a day.

The Verrazzano fact is the keeper: build anything long enough, and the curve of the Earth itself shows up in the blueprints.