For the 1,600 police officers who guard the Capitol, the 19th-century building is a logistical nightmare.

Every room is different, every staircase is worn. Continuous expansions and renovations have created a maze of connecting offices, hidden doors and underground tunnels.

And yet Capitol Police officers rarely train in the environment that they are sworn to protect. Aside from the rare on-site exercise, they use classrooms to run drills, pretending that the mat-covered rooms are sections of the 200-year-old Capitol.

Soon, however, the department will complete its Practical Application Center, a $17.5 million building that allows officers to train in rooms that replicate parts of the Capitol. Already, police instructors are using the finished parts of the building to train recruits.

“Training is very important to law enforcement. Being able to train in an environment in which we work is critical,” Capitol Police Chief Phillip Morse said. “We have just about everything here.”

The facility is one of the largest improvements to the department’s training regimen in decades.

Few police departments have something comparable. One of the most impressive is the Secret Service’s “Hogan’s Alley,” a city block of building facades where agents practice shooting pop-up cutouts of assassins.

The Capitol Police facility is more focused on the Capitol and measures only 41,000 square feet. Surrounded by woods in Cheltenham, Md., it sits next to the department’s other training facilities, including a gun range and a classroom building.

On a recent Tuesday, Morse led a group of officers on a tour. As members of the Chief’s Advisory Council — a group that makes recommendations to Morse — they were the first officers to see the near- complete building.

While the facility’s facade resembles a small-town office building or a college dorm, inside it is akin to a carnival funhouse. One room resembles a restaurant, while another down the hallway is a mini-version of the House floor and gallery.

Eventually, video cameras will line every room and hallway. Instructors will be able to fill rooms with smoke, lock doors at the push of a button and review a scene from several different angles. Officers, meanwhile, will be able to shoot each other with simunitions, wax bullets that make a mark like paintballs.

On the tour, the officers were visibly excited. The advisory committee includes representatives from almost every department — patrol, intelligence and K-9 among them — and several found features that would help them prepare for their jobs.

K-9 Officer Jim Davis said the facility will help train police dogs in different environments. Now, officers have to find abandoned warehouses and available venues to train their dogs, often using sites such as RFK Stadium and Nissan Pavilion.

The new facility, Davis said, will let him train his German shepherd, Darko, to handle an environment much like the Capitol. That way, he said, he can better gauge how the dog reacts when he senses explosive material.

“We train in different areas to give dogs as much” exposure to different situations as possible, he said. “Until they get exposed to it, you don’t know what they’re afraid of.”

At the new facility, Davis will be able to introduce Darko not only to a chamber floor, but also to the Upper West Terrace, hotel suites, offices and a grand staircase with the same worn grooves as those in the Capitol. Nothing looks exactly like the original; most rooms have concrete floors and lack the details of the ornate Capitol.

Still, the rooms include all the necessary features. In the hotel suite, the tension on a plywood door can be adjusted so officers can practice kicking it open.

On the recent tour, instructor Sgt. Elton Mobbs dared officers to showcase their strength.

“Wanna give it a kick?” he asked.

Without a pause, Officer Edward Jackson kicked it open and ran inside, followed by Morse and rounds of laughter.

Being able to kick open a door — without worrying about destroying it — is critical to training.

In the Capitol, Morse said, there are “obviously a lot of historic factors that need to be preserved. You can’t destroy those things with training.”

But the training facility is meant to be abused by officers kicking open doors, shooting fake bullets and jumping over furniture.

“It’s whatever situation or sequence you want to create for the unit that you’re training with,” he said. “It’s really open to whatever you want to do.”