Vertigo alert:

Tomorrow at 10 a.m. ET, the Skydeck at Chicago's Sears Tower opens four glass-bottomed observation bays that let folks willing to pay $14.95 ($10.50 for kids) stand 1,353 feet above the city.

On a clear day, if you have the nerve to step on to the glass, you can see 40-50 miles.

On NBC-TV's The Today Show this morning, correspondent Kevin Tibbles went out on "the ledge":