The first episode of “House of Cards” second season left viewers with many questions. For those familiar with D.C., one question revolved around the fictional Cathedral Heights Metro. In a word: Why?

“Cathedral Heights” was the site of a major (and spoil alert-inducing) scene for season two of the popular Netflix drama. It was actually shot at the Charles Street subway stop in Baltimore, where much of the filming for “House of Cards” is done. Loyal viewers of the series will remember that last season featured an actual D.C. Metro scene, filmed at the Archives-Navy Memorial-Penn Quarter Metro station.

“House of Cards” isn’t the only D.C.-set production to use or reference a fake Metro station. There’s the uncharacteristically well-lit Union Station on “Scandal,” the dubious Meridian Hill stop and the close-but-no-cigar Farragut Station on “Homeland.” And for all you Kevin Costner fans out there, there’s that  Georgetown Metro station in the 1987 film “No Way Out.”

“Scandal,” is unabashedly filmed in Los Angeles, Showtime’s “Homeland” in North Carolina. But for scenes shot in driving distance of the nation’s Capital, why not make the trip in the name of authenticity?

“Many times it’s just a question of logistics,” said Maryland Film Office Director Jack Gerbes, adding that safety is of particular concern on transportation-related shoots. For the “House of Cards” scene, the filmmakers worked with the Maryland Transit Authority, employees of which were required to be on hand during filming. Shooting locations must also provide enough space for filming equipment, including trailers that can often span blocks.

Debbie Donaldson Dorsey, director of the Baltimore Film Office, credits “a solid infrastructure and cooperative city agencies” for bringing film crews to Baltimore. Dorsey said the MTA has been particularly welcoming to production companies. For television shows especially, “things need to happen within a couple of days,” Dorsey said. “There’s no red tape at all. It’s Scotch invisible tape,” she joked.

It doesn’t hurt that Maryland offers attractive tax incentives for filmmakers. Gerbes said that the tax credit for 2014 would be 25 percent of costs incurred in the state for an episodic television production like “House of Cards.” If a production were to leave the state for a day to film in D.C., they would not be eligible for the tax credits on that day. It’s unclear whether those  incentives will extend to further seasons of “House of Cards” — the show recently threatened to move production if it doesn’t receive millions more in tax credits.

Filming is allowed in the D.C. Metro system, but there are various fees (in addition to permit and insurance costs), and a list of rules, including guidelines on the types of scenes that can be filmed.

“We reserve the right to approve or deny commercial filming requests following a review of the script,” Morgan Dye, a spokeswoman for the Washington Metropolitan Transit Authority, said in an e-mail. Essentially, if you can’t do it on Metro, you can’t do it on TV. That means no running, for instance, so chases like the one in the aforementioned Costner film are out (that, too, was filmed in Baltimore).

Panhandling is prohibited by Metro rules, so filming “Scandal’s” recurring flashbacks to Huck’s days in Union Station wouldn’t fly either.  Sorry, Marion Barry.

Patrick Burn, location manager for the first and second seasons of “House of Cards,” said that the D.C. Metro “generally has some of the same issues that all metros have,” which in addition to safety precautions includes ensuring that filming doesn’t interrupt service. Burn, whose film career includes a stint at D.C’s Office of Motion Picture and Television Development (MPTD), also worked as a location manager for D.C.-set films including “Salt,” and “True Lies.”

While preparing the season two Metro scene for “House of Cards,” the production team had to describe the scene in detail for MTA. “Their concerns were safety related,” Burn said. “They were actually very helpful…they really bent over backward for us. We had the same experience in D.C. when we filmed there.”

In general, filming in D.C. presents a unique set of challenges, said Leslie Green, communications director for MPTD. For one, D.C. lacks the state-funding that draws filmmakers to places like Maryland and North Carolina. Production companies also have to coordinate with multiple entities on the district and federal level, which could include groups like the National Parks Service, the Capitol Police or multijurisdictional agencies like WMATA, which has final say over what can or cannot be filmed on Metro property.

While both “House of Cards” and “Homeland” have filmed “establishing shots” in D.C., choosing a filming location often comes down to cost,” Green said. “At the time, the District just could not compete with states that were throwing millions of dollars at these production companies to shoot there.”

Green said MPTD’s new director, Pierre Bagley, is working with city officials to combat the perception that D.C. is a difficult place to film. The District currently has just around $4 million in its film incentives fund, and while allocation plans are not complete, Green said some of the money will be used for the local film industry, which could include D.C.-based filmmakers and production companies that are based in the District or choose to relocate there.

“I think folks are really hopeful about being able to create more of an opportunity here for the local film community,” Green said.

This post incorrectly stated that Showtime’s “Homeland” airs on HBO. The post has been corrected.