What if I told you one of Portland's bridges was an engineering marvel of its era that's not just the largest and heaviest bridge built on the Willamette, but also a world-record holder?

Any guess which bridge I'm talking about?

The answer is the Burlington Northern Railroad Bridge 5.1, which was completed in 1908 at a cost of $1 million and had the largest single-span drawbridge in the world at the time. If the name of that bridge doesn't ring a bell, it's because it's a railroad bridge between the Fremont and St. Johns bridges that's forgotten by most people. If you've crossed it, it's almost certainly been on the Amtrak train to Seattle.

I crossed the bridge for the first time in January, and boated under it in June. Both times I was struck by its isolation and industrial-age beauty, like something out of Detroit-ruin porn tucked into the industrial fringes of the city. The Burlington Northern bridge (which is 5.1 miles downriver from Union Station) looks like a beefed-up Steel Bridge, but is colored in a calico of black, green, silver and rusty red. It's framed by the West Hills on one side and the University of Portland neighborhood on the other. There's nothing in particular near it but the bluffs and a massive grass prairie surrounded by barbed wire that, legend has it, was once a party pit for UP students. Those kids had a wonderful view of a secret bridge most Portlanders have forgotten exists.