I'm generally not fond of big downhills in city centers.
My worst crash was at the bottom of a hill in San Francisco where the city had decided not to raise the level of the manhole cover to the height of the regraded surface. Only time I've ever actually flown over the handlebars.

Not a common situation, which is probably why I didn't know that black manhole cover on black tar street actually camouflages the grade difference when you're approaching downhill.