A 100-mile bike ride is called a "century" and a 65-miler is sometimes referred to as a "metric century."
I had thought this would become one of the hardest things I'd ever done, but was pleasantly surprised - it was hard, but not horrible. The whole thing was done in 4.5 hours! Of course it helped that the Chico Wildflower run has lots of rest stops with great food. :) Definitely filled me with the ambition to do more long rides like this - hopefully next time for charity.
Full set of notes and pics here.
Next up: Full Century! (100 miles)