The $20 million jewel of the terminal

To most visitors, the clock atop the Grand Central main information booth is nothing more than an attractive time piece. But in fact (and this is the second secret that's part of the Information Booth), its four faces are made from extremely valuable opal, and the clock has been appraised at around $20 million.

Click here to read the related behind-the-scenes story on the secrets of Grand Central Terminal. And click here to check out the entire Road Trip 2010 package.