The Steven F. Udvar-Hazy Center is an annex to the Smithsonian National Air and Space Museum in Washington, D.C. Often called the NASM's companion facility, the Udvar-Hazy Center is also known as the Air and Space Museum Dulles. 

While the Udvar-Hazy Center may be lesser-known than its counterpart on the National Mall in D.C., it is packed with numerous unique things to do and see, including the Concorde and Space Shuttle Enterprise display. However, there are many more surprising — and really cool — things to discover about the Udvar-Hazy Center. Here are the top five.

1. It's Free 

Admission to the Udvar-Hazy Center Air and Space Museum Dulles is completely free. There is a charge for parking, but no tickets are required, and everything is free, including guided tours led by knowledgeable and enthusiastic staff. 

2. The "Space Backpack" is on Display

One of the most iconic images of astronauts is that of Bruce McCandless floating through space, just him and what looks like a backpack against the pitch-black backdrop of outer space. That backpack is actually a Manned Maneuvering Unit (MMU), a propulsion system that enabled astronauts to fly independently of a spacecraft. It's been on display at the Air and Space Museum Dulles since 2001, and because it's situated above and to the side of the Enterprise, it's easy to miss. 

3. Watch Restoration in Action

Museum visitors are able to watch restoration specialists repairing and preserving artifacts from a mezzanine in the Mary Baker Engen Restoration Hangar. Previously this type of work was done only in facilities that had limited access to the public. 

4. Home to the Fastest Jet in the World

The Lockheed SR-71 Blackbird has an incredible history, and it's found a home at the Air and Space Museum Dulles. Originally highly classified as a "black project," the SR-71 was used primarily by the U.S. Air Force for high-altitude reconnaissance missions during the Cold War. On its last flight in 1990, the Blackbird set a world speed record by flying from Los Angeles to the Smithsonian in Washington, D.C., in 1 hour and 4 minutes, at an average of 2,124 mph.

In more recent history, people may recognize this particular Blackbird as the Transformer "Jetfire" from the 2009 movie Transformers: Revenge of the Fallen. Scenes from the movie were filmed at the Udvar-Hazy Center, and there is a display dedicated to its filming.

5. Enjoy a 360-Degree View of Washington Dulles International Airport

Few places in the world offer this type of perspective, but the Udvar-Hazy Center does. From the Donald D. Engen Observation Tower, museum visitors can watch planes land and take off with a bird's-eye view of the entire surrounding area and learn all about how the air traffic control system works. 

For true aviation aficionados, a visit to the Steven F. Udvar-Hazy Center Air and Space Museum Dulles is a real treat. It's only slightly out of the way and offers some truly one-of-a-kind experiences. (For more space info, please click here.)