Heading west on U.S. 64 from the “old blinking light,” you pass the Taos airstrip on the left, and then, after a few more miles, the ground simply drops away. This is the Rio Grande Gorge, plunging 800 feet deep in malevolent-looking black basalt at its most alarming point.

The river winds below, but it’s not just millions of years of rushing water that have carved out the canyon—seismic activity has also caused a rift in the earth’s surface. The crack extends north to just beyond the Colorado state line and south almost to Española.

The elegant, unnervingly delicate-looking bridge that spans it was built in 1965 to supplement entrepreneur John Dunn’s rickety old toll crossing eight miles north. Critics mocked it as “the bridge to nowhere” because the highway on the western bank had yet to be built, but the American Institute of Steel Construction granted it the Most Beautiful Span award in 1966. At 650 feet above the river, it was, and still is, the second-highest bridge in the United States (after the Royal Gorge Bridge in Carñon City, Colorado, and the New River Gorge Bridge in West Virginia).

On either side of the bridge is the stretch of canyon called the Taos Box, two words that will inspire wild tales in any seasoned river runner. The Class III and IV rapids, which start around John Dunn Bridge to the north, are held to be the best place for white-water rafting in New Mexico.