I've been to almost 10,000 feet on Rainier. Walked on a glacier.
Good enuff for me! Still got my fingers and toes.
My mother climbed Rainier in the early 60's. Tried and failed once, tried again and made it to the top. It was a moment she remained proud of till she died.
There are a number cable car gondola lifts which can take you higher around the world. I went on the one in Chamozix France which took me to around 12,500 feet. At that height I found simply climbing steps winded me. Here is a list of the top 20 http://www.natives.co.uk/news/2001/0501/03highestlifts.htm