tiny humans exerting themselves to make their way to the top of large heaps of rock, for no rational reason.

Mount Everest is probably one of the most famous mountains for being climbed, given that it is the world's tallest mountain.

Mount Blanc, Mount Elbrus, Mount Rainier, and lots more might be fun to climb, too.

Mount Sumeru and Mount Doom would be kind of hard to find..

it would not be a good idea to try to climb Mount Rushmore.

Mount Vernon isn't a mountain at all, but since this writeup is already off-topic, how about a shameless ploy for traffic, with a link to 'mount'. ('cause sex sells!)