A thousand metres of climbing without a break is where a ride stops being a ride and becomes a day. No col to crest, no valley to roll through, no stretch where the pressure comes off your legs for long enough to matter.
Haleakalā is the extreme case anywhere on Earth: three thousand metres from a beach on Maui to the rim of a crater, in one go, with the vegetation changing under you the whole way. Mount Lemmon starts in saguaro forest outside Tucson and finishes in pine. Beartooth spends its last hour on a plateau among alpine lakes, above everything.
Pikes Peak and the Stelvio need no introduction.