The protesters ambled about for a moment. Then squatted on one of the grand, marble staircases. One hoisted a sign, printed in green marker. As if on cue, they began to chant “Health care now! Health care now!”

Within a few moments, a team of U.S. Capitol Police officers swarms the covey of protesters and forms a human perimeter. A lieutenant steps forward to address the group.

“You are in violation of the law, demonstrating in (the) U.S. Capitol Building. You are ordered to cease and desist at this time or you will be subject to arrest,” the officer barks.

The chanting halts for a moment. But then the protesters resume their verbal assault. The officers again inform the group that if they continue, they’ll be arrested. But after a final warning, one of the protesters tells the officers he wants to be arrested.

And out come the plastic flexi-cuffs.

The officers handcuff the protesters. And then one by one, help them down the grooved stairs, each bowed in the middle from nearly 150 years of human foot traffic.

But after the officers lead the suspects around the corner, the police immediately take off the flexi-cuffs and release their prisoners.

It may look like a health care protest. And the scene may even look like the U.S. Capitol. But it’s not. The police are real. But the protesters are actors portraying parts in a training exercise for the U.S. Capitol Police.

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The FBI has “Hogan’s Alley,” a tactical training facility in Quantico, VA, that resembles a city street. It’s complete with a post office, barber shop and pool hall. And like the G-men, the Capitol Police have their own training center that mimics key parts of the unique environment that they patrol on Capitol Hill.

Located just south of Washington’s Beltway in suburban Maryland, the Capitol Police training center resembles a Hollywood soundstage. It’s stocked with scenery and props that replicates the House chamber (featuring a dais and public viewing gallery), a model of a Congressional office, imitation guard shacks and steel barricades that look like those ringing the Capitol and historic staircases. Right down to the grooves in the marble.

The Capitol police say the simulations are essential training tools to coach their force for their very specialized form of law enforcement.

“Having a replica of the House floor where the House conducts business gives the officers a good idea, once they get to the Capitol, what they’re going to be doing and the importance of what they’re going to be doing,” says Officer Terry Hughes.

And the drills the cops rehearse here are similar to arranging a stage play.

“You have a number of different venues that replicate situations that you’re going to be in on the Hill,” said Sgt. Elton Mobbs, one of the main trainers at the facility. “All of the scenarios are scripted.”

The officers duplicate sequences that they could encounter on the job. For instance, one drill simulates a disruption in the public viewing gallery of the House chamber. One officer portrays a member of Congress delivering a speech. Meantime, another officer acts as though she’s the Speaker of the House, presiding over the debate. The police don’t intervene in the melee until given orders by the House Speaker.

The physical props are critical, too. And they enable the police to rehearse everything from inspecting vehicles to uncovering a weapon that someone could try to sneak into the Capitol. The officers even keep an old coffin on hand to help the ceremonial unit train for state funerals in the Rotunda.

“It just makes them more confident when they go out there,” says Sgt. John Booth of officers who practice at the facility.

Terry Hughes says new officers really have to get used to the different type of policing they do on Capitol Hill.

“We almost don’t want to be noticed most of the time,” says Hughes. “What we do is in a very politically-charged environment. What we do has to be as low-key as possible.”

U.S. Capitol Police may try to be low-key. But they are a show of force everywhere you go around the Capitol complex. Some officers may be assigned to guard House Speaker Nancy Pelosi (D-CA), second-in-line to the presidency. Others are stationed outside the House and Senate chambers. Some are on road patrol, driving the streets that loop around the Capitol. And others scour through the bags and purses of thousands of staff and the public who enter into the House and Senate office buildings on a daily basis. The officers aren’t invisible. But their presence is a not-so-subtle reminder of the dimension of the threat the Capitol faces.

Many now forget that the fourth airliner hijacked on 9-11 was bound for the U.S. Capitol.

It’s only when the U.S. Capitol Police are pressed into service that the unique drills they practice at their training facility are put to use. And the result is often anything but low-key.

Last summer, Capitol Police tried to pull over a motorist driving a stolen vehicle near Union Station, Washington’s train depot in the shadow of the Capitol. The driver then sped away, injuring two other officers nearby, including one involved in another traffic stop. The driver then dodged traffic and tore the wrong way down Louisiana Avenue on the Senate side of the Capitol, U.S. Capitol Police cruisers in hot pursuit. The suspect then veered toward an underground garage where thousands of Senate staff and lawmakers park their vehicles. The driver then crashed. And as officers converged on the car, the suspect began shooting at police. They returned fire, killing the suspect at close range.

Not exactly the routine rummaging through backpacks and checking ID badges that goes on all day around the Capitol.

Nor was the scene routine in July, 1998 when a deranged gunman named Russell Weston Jr. entered the Memorial Door on the east side of the Capitol and unleashed a hale of bullets. Weston immediately killed Officer Jacob Chestnut at the entryway and made a quick left, toward the office suite of then-House Majority Whip Tom DeLay (R-TX). That’s where Weston shot Detective John Gibson, a member of DeLay’s security detail. Gibson later died. But not before getting off a shot that critically injured Weston, ending the terror.

Weston would have died had former Senate Majority Leader Bill Frist (R-TN), a heart surgeon, not saved his life. Doctors later declared Weston mentally unstable. He’s never stood trial.

Officer Chestnut and Detective Gibson remain the only persons ever killed defending the U.S. Capitol.

Chestnut and Gibson never got to train at the unique building that duplicates portions of the Capitol complex. It’s a new facility that just opened over the past year. And it’s named after Officer Christopher Eney , who was killed during a mid-1980s training scenario. Eney was the first member of the U.S. Capitol Police to ever die while on duty.

“It works a lot better than (officers) having to just imagine what it must be like (at the Capitol) and for us trying to tell them as best we can,” says Capitol Police trainer Elton Mobbs of the special building, that bears Eney’s name.

Grooved stairs. Narrow hallways. A cavernous room reminiscent of the House chamber. These are all part of the training facility Capitol Police use to prepare for their specialized type of policing: protecting one of the most-famous buildings in the world. One of the most threatened buildings in the world.

-         Chad Pergram covers Congress for FOX News. He’s won an Edward R. Murrow Award and the Joan Barone Award for his reporting on Capitol Hill.

-          The Speaker’s Lobby refers to a long, ornate hallway that runs behind the dais in the House chamber. Lawmakers, journalists and aides often confer there during votes.