Altitude means to me 'above sea level', so I tried to think of the highest elevation I have ever been to, at 11,500 to 12,000 ft.

it has to be Yankee Boy Basin near Ouray, Colorado. It is known for it's wildflowers:

A video of a drive up there, for 4 wheel drive vehicles only.

This is where we spread my Aunt Jody's ashes in July 2006, she passed Feb. 6th. We had to wait until the snow melted up there. My Dad flew out from Australia. We, along with 5 of Jody's friends, loaded in to 2 x 4WDs to get up there. We mixed wildflowers seeds in with her ashes before we strew them around the field that we recognized from a photo of Jody's.