Results: Shhh...Don't Tell! (Part 2 of 6)

Empire State Building, New York City, New York - An Art Deco icon in the Big Apple, the Empire State Building is one of the most famous skyscrapers in the world – so you might think you know all its secrets. You'd probably be wrong, though. While many think the 102nd-floor observatory is the loftiest viewing deck the building has to offer, there's also a top-secret balcony on the 103rd floor reserved for VIP visitors. Celebrities including David Beckham have been snapped enjoying the view from this elusive spot. Were you aware of this secret?

Hoover Dam, Nevada/Arizona - This enormous concrete dam was built in the 1930s to help tame the Colorado River and relieve the surrounding areas from constant flooding. Fast-forward nearly nine decades and the dam is a major tourist attraction with a horde of secrets that many of its visitors might not know. One little talked-about fact is that Hoover Dam is surrounded by dive sites – a warren of shipwrecks and ruins that exists beneath Lake Mead's surface. Advanced divers can spot train tracks and even explore concrete tunnels around a hopper used in the dam's construction. Were you aware of this secret?

The White House, Washington DC - It's no secret that the White House is large and lavish, home, of course, to the Oval Office, the painting-clad Cabinet Room and the Executive Residence. Yet there are a few rooms that may surprise you. The presidential residence also boasts a cinema, tennis courts and even a bowling alley. There's also apparently a little-known alleyway leading to tunnels that serve as a discrete entrance to the White House – and rumors of many other secret passageways besides. Were you aware of this secret?

William Penn Statue, Philadelphia City Hall, Philadelphia, Pennsylvania - A bronze statue of Philadelphia's founder, William Penn, or Billy Penn as he's affectionately known, has looked out from the top of City Hall since the late 1800s. Penn has become an icon of the Philly skyline – but he's hiding something. The statue of Billy Penn is actually hollow and, over the years, has been used to hold TV and radio antennae. There's also apparently a small hatch at the statue's peak, so you can poke your own head right through the top of Billy's. Were you aware of this secret?

875 North Michigan Avenue, Chicago, Illinois - Chicago is well-known for its skyscrapers and one of the most striking is antenna-topped 875 North Michigan Avenue, formerly the John Hancock Center. The 360 Chicago Observation deck is a major draw, offering fabulous views of the Windy City, but there's something super swanky on the 44th floor too. Accessible only to residents of the tower, this floor is home to a mammoth superstore, a library and even a sleek swimming pool with jaw-dropping city vistas. Were you aware of this secret?