I’m an investigative reporter, so I have an affinity for parking garages.

But even those who are not drawn to the ubiquitous structures professionally (gangsters, smokers, stalkers — nothing uplifting ever takes place in a parking garage) will find the new parking garage exhibit at the National Building Museum thought-provoking, precisely because it asks us to think about something we never think about.

Or more to the point — we think about PARKING all the time, several times a day. A journey by car almost always begins with the question, “Where will I park?—

Nevertheless, we rarely give any thought to how any particular parking garage got there, why it is laid out the way it is or who designed it.

The Building Museum exhibit “House of Cars: Innovation and the Parking Garage— attempts to tackle these questions and offers a bit of homage to the structures that have been such an overlooked part of our cultural landscape.

Curator Sarah Leavitt said that as a graduate student in American studies at Brown University, she was a teaching assistant for a class about “the automobile and American life,— a common topic for cultural studies around the country. “But we never talked about parking at all,— Leavitt said. “How can you possibly not talk about parking?—

The exhibition sets out somewhat chronologically. The first parking garages arrived about the same time cars did, and they were generally built to look like regular buildings, with windows, facades, the whole bit.

By the 1950s, the walls were stripped away, and the structures became a series of functional concrete ramps and landings, wrapped with low railings, and maybe an electric sign advertising “Parking.— Visit any old industrial city in the U.S. and you will still see these old gap-toothed structures plunked in between the office buildings and shops downtown. Many of these old decks have been torn down and replaced by office buildings with underground parking. The old concrete deck is something of an endangered species — in fact, according to Leavitt, more than a dozen parking garages are on the National Register of Historic Places.

The exhibit follows the evolution of parking structures through a series of cultural evolutions. In recent years, we have tended to build parking garages behind things or under them (with the embarrassing exception of the Washington Nationals, who built parking garages between the new ballpark and the scenic view of the Capitol). But there have always been design questions to address: straight parking or angled? Spiral ramps? Attended or unattended lots?

Some older garages used electric lifts to stack cars in honeycombs so that the driver didn’t have to search for a space, but that technology fell out of favor in the middle of the last century. Now it is returning as a way to save space and cut down on wasted driving. The exhibit also looks at parking garages of the future, as modern designers add whimsy and environmental consciousness into the facilities. After all, these are large public buildings; why not have one that lights up when a person drives in?

There is also a move to build more environmentally sound parking garages — solar panels powering the lights, runoff controls for the icky rainwater that trickles between the vehicles, etc. — though there is some dispute in the environmental community about whether that is an oxymoron. Leavitt says that thus far, three parking structures have been certified as “green buildings,— so it is now at least theoretically possible to pave paradise and put up a parking lot with conscience.

As with many Building Museum exhibits, “House of Cars— is long on interesting concepts and a little short on fun stuff to look at and play with. But the curators have assembled a spectacular 15-minute video of Hollywood clips that feature parking garages, in everything from “The Love Bug— to “The Dark Knight— to, of course, “All the President’s Men.— Leavitt said the museum is also planning a film series in February and a lecture series to further explore the role of the parking garage in American culture.

And here is where I can admit that I did once meet a source in a parking garage, but I swear it was his idea, not mine. He wanted to leak some strategic planning documents the Environmental Protection Agency had drafted — a nice story for the publication I worked for at the time, although hardly the Pentagon Papers. But he wanted the thrill of the clandestine handoff, and I didn’t have the heart to tell him the EPA parking garage was probably the single most conspicuous place we could meet. If you want to have a clandestine handoff, do it in the vegetable aisle at Safeway, where it is not unusual to see random people milling about, not in the shadows of a parking lot, where every passerby (1) notices you and (2) thinks about calling the police.

But whatever, he wanted to play Deep Throat, and that made me Bob Woodward (or maybe even Robert Redford), so I met him in the EPA parking garage. And no, the EPA administrator did not come tearing around the garage in his Lincoln Town Car, tires squealing and guns blazing. Hollywood lies about a lot of stuff.

“House of Cars— is on exhibit at the National Building Museum through July. Take Metro — the museum has no parking garage.