When Pierre Charles L’Enfant was designing the city of Washington, D.C., he staked out a hill that stood 88 feet above the Potomac River’s surface and dubbed it “a pedestal waiting for a monument.”

On that pedestal now stands the Capitol building, which has served as a working monument and celebrated attraction for visitors and locals since President George Washington laid the first cornerstone in 1793.

With the addition of the 580,000-square -foot visitor center, the Capitol now houses a museum designed as a millennium-era attraction and complement to the monument on the hill.

“The design is modern but faithful to the grandeur of the Capitol,” said Andrew Goldberg of the American Institute of Architects. “The Capitol is not just any building. It’s an historic place, and there are security concerns. The design challenge is to address all those aspects at once.”

The Capitol Visitor Center is the first major addition to the Capitol since 1962, when the building’s East Front was extended 32 and a half feet.

The CVC, whose public space is the size of five football fields, took six years to complete. It has a footprint that is 193,000 square feet, substantially larger than the perimeter of the Capitol itself.

The visitor center was constructed below the Capitol’s surface; guests must travel down a set of stairs to find the entrance.

“You think you’re getting to a dark space, but actually it’s something else,” said Terrie Rouse, the CVC’s chief executive officer for visitor services.

The surprise is Emancipation Hall, named to recognize the slave laborers who built the Capitol in the late 18th and early 19th centuries. It is bright and open and unlike anything in the ornately painted and highly traditional Capitol.

Two 30-foot-by-70 foot skylights dominate the hall and provide a clear view of the Capitol Dome.

“It’s an extension to the building, but it doesn’t take away from the building,” Senate Associate Historian Don Ritchie said, noting that the visitors’ focus is drawn upward toward the Dome.

Goldberg, who visited the CVC during various stages of its construction and called the finished work “fantastic,” said designing a space to add to such an historical site is a tremendous challenge for any architect.

“The goal is to bring out the subject, not overpower it with anything too glitzy,” he said. “Nothing will ever replace the Rotunda, so instead you bring another context to the Capitol itself.”

If Emancipation Hall shows the grandeur of the Capitol Dome, then Exhibition Hall explains it. The 16,500-square-foot space is a small nook in the huge CVC and contains the artifacts and stories of the Capitol. Unlike Emancipation Hall, the exhibit area is dimly lit and has a familiar feel.

“It draws people in from a vastness to an intimate level,” Rouse said.

Spokesmen expect the CVC to attract nearly 3 million visitors in its first year, and Ritchie said the new building gives tourists “a fighting chance to get to know what goes on in the Capitol before they enter it.”

A 20-foot plaster model of the Statue of Freedom stands just before the entrance to Exhibition Hall, followed by an 11-foot replica of the Capitol Dome. Exhibition Hall tells the story of Congress and features copies of legislation establishing the Navy in 1798, abolishing slavery in 1865 and creating Social Security in 1935.

“It’s the only [museum] focused on Congress. When the American History Museum talks about politics, it’s always about the presidents and first ladies,” Ritchie said. “Congress isn’t easy to portray, [and] this shows the evolution of the institution.”

Indeed, virtual tours of the Capitol’s private rooms and scaled-down replicas of the House and Senate rostrums give visitors an inside look. The building’s evolution is chronicled in a series of miniature models, which also show the growth of the Capitol Hill neighborhood.

Construction near the Capitol has been a delicate issue going back to the 1850s, when the House and Senate wings were added.

Much like the CVC, which was completed years behind schedule and several hundred million dollars over budget, critics have long assailed the cost and length of Capitol projects.

But as a public building and working monument, the latest Capitol addition will likely be a celebrated one.

“Some wanted the House and Senate wings to be scaled down. Others wanted a more ornate look,” Ritchie said, adding “Some day people will probably consider the visitors center a natural addition.”