Unable to plan another awesome interior atrium (like his Hyatt Regency Atlanta) due to lots of restrictions, the architect John Portman used ten huge cylinders to support the fifty-six floors. The employment of space, form and materials is astounding -- with a focal point centered around refreshing indoor "lagoons." Again, like the Hyatt Regency, a revolving restaurant tops the brilliant complex. (Adapted from A Field Guide to Landmarks of Modern Architecture in the United States by Miiam F. Stimpson)