What are some examples of objects the size of a kilometer?

Your Mom!

Just kidding.

The world's tallest buildinghttp://wiki.answers.com/wiki/Burj_Khalifa, is .82 kilometers tall. By comparison, Mount Everest is the Word's tallest mountain and stands at 8.8 kilometers above sea level.

Objects closer to 1 kilometer are the height of Niagra Falls (1039 meters, or 1.039 kilometers).