As the muni yield curve steepens investors will start interpreting that steepening as a reflection of increased risk.

FORBES: Move Over Treasuries, Muni Bonds Are The New Bellwether

But the Albula steepens quickly, and the river disappears into a dramatic ravine, forcing the train to criss-cross the gorge, creaking like a sailing ship in a full-bellied wind.

BBC: Full steam ahead