So, you can run 26.2 miles on the ground and think you're pretty hot stuff, huh? How do you think you would fare if you had to take your race in an upward direction?

Though you might not have tried it, vertical marathons are actually fairly common. On November 15, if you're in the Chicago area, you can take part in Skyrise Chicago Tower Up at the Willis Tower. With 2109 steps, you'll be climbing North America's tallest set of stairs, and you can climb by foot or by using specially installed hand cycles. And lucky you -- they're still accepting registration!

The following weekend, Swissôtel Vertical Marathon 2009 lets you race to the top of one of Southeast Asia's tallest hotels, located in Singapore. Last year, a new record for climbing the 73 stories was set at six minutes, 52 seconds. Think you can beat it? Registration for this year is closed.

Looking for the tallest stair climbing race in the world? Try the Radebeul this April, which is a double marathon located in Germany. You'll cover a horizontal difference of 84,390 meters, and a vertical distance of 8,848 meters. Registration is open and they'll keep a waiting list open. I'm not going to lie -- they'll be waiting a long time before I sign up for this one.

If you'd prefer to remain Stateside, you've got lots and lots of options. Chicago has more stair races for you, and, unsurprisingly, New York offers a race up the Empire State Building as well as Rockefeller Center. Out West, you can climb in Los Angeles, San Francisco, or have your choice in Seattle, Washington. There are plenty more, ranging from Detroit to Miami to Phoenix -- you're sure to find a vertical marathon that's near you!

You think completing these races is impressive? Check out ultra endurance!