Everyone knows the famous sites, the Washington Monument, the Lincoln Memorial, the Capital Building, and obviously, the White House. But Washington, D.C. has many more lesser known sites, even obscure, that have an interesting history and are worth visiting, or at least a quick look in the case of those sites that now operate as something else.

Washington Coliseum

In what is now a barrel-shaped architectural ruin just north of the Capital on 3rd Street NE, at 8:30 p.m. on February 11, 1964, the Beatles played their first stage concert in the U.S.

It was built in 1940 and 1941, and has since served as an ice rink, sports arena, worship hall, trash transfer station and parking garage. It has hosted numerous professional sports teams and was at one time home to the Ice Capades.

Malcolm X and Elijah Muhammed spoke there.

But for Beatles devotees, that concert was a seminal moment.

Courtroom

In this room, testimony was heard against John Wilkes Booth.

"I was acquainted with John Wilkes Booth," said Peter Taltavul, a tavern owner.  "Booth came into my restaurant [adjoining Ford's Theater] on the evening of the 14th of April."

"Booth "walked up to the bar and called for some whiskey, which I gave him, he called for some water, which I also gave him," said Taltavul.  "He placed the money on the counter and went out."

"I saw him go out of the bar before I heard the cry that the President was assassinated."

At the time of the testimony, Booth had already been killed by authorities, and eight people believed to have helped him had been arrested. A military commission was convened to conduct a trial in the third floor of what was, at the time, a federal penitentiary. All were found guilty on July 6, 1865, and hanged the next day.

The penitentiary is now closed and mostly demolished, but the land is part of Fort McNair at the southernmost point of Washington.

Visitors are often overwhelmed.

"There's no substitution for actually witnessing or being in the middle of a historic site like that," Susan Lemke, a special collections librarian, told CNN.

Gallows

On the edge of a tennis court at Fort McNair, near the penitentiary room where the sentences were handed down, those accused of assisting John Wilkes Booth in the assassination of President Abraham Lincoln were hanged under the direction of Captain Christian Rath.

"I am one of those people who think that if you really want to understand history, you have to go to where it happened," Kauffman, an expert of the Lincoln assassination, said.

Today, the penitentiary's tall wall has been demolished and a building that was prominent in the photographs of the hanging has been altered almost beyond recognition.

"There's this strange sort of excitement that you get when you've read about something, and you visualize it, and you think you know all about it, and then all of a sudden you go there and it's right in front of you," Kauffman said. "It surrounds you.

"And it's always somehow different from what you had imagined," he said.

Chadwicks was the site of the infamous "Big Dump."

Chadwicks

In an event on June 16, 1985, known as "the Big Dump," CIA officer Aldrich Ames walked into Chadwicks, a pub in Georgetown, with two bags full of classified information and gave them to a Soviet diplomat over lunch.

"In those bags was every piece of paper he could get his hands on that revealed almost all of our operations in the Soviet Union," said Peter Earnest, a former CIA official who is now executive director of the International Spy Museum in D.C.

The breach wasn't discovered until the Soviet Union began rounding up the most valuable assets the U.S. had is Russia, where at least 10 were executed.

Ames and his wife were arrested, but not until 1994, nine years after the Big Dump.

"The repercussions of what he did ripple through the government today, the need to have more polygraphs, the concerns about our records, the nature of the questions asked," said Earnest.

Alexandria Slave Pen

The building known as the "Alexandria Slave Pen"  on Duke Street still stands in Alexandria, Virginia, just across the river from Washington.

"I often tell my students, 'You've gone into towns where you just see row after row of car dealerships," Chandra Manning, associate professor of history at Georgetown University said. "Duke Street was that, but slave dealerships."

In May of 1861, the Union Army marched into town, and liberated the slaves, at which point, the slave pen became a refuge for runaway and freed slaves seeking the protection of the Union Army.

Today, 1315 Duke Street is the home of the Alexandria branch of the National Urban League, a civil rights organization.  Ironically fitting, no?

A historical marker stands outside, and there's a small museum in the basement, but most passerby are unaware.

"If you're walking with me you have no choice but to know what happened here," Manning said. 

The Forgotten Crash

On a foggy night in 1906, a train was running down the tracks near Catholic University at the same time as a slower passenger train was going the opposite direction on the same track. There was no time to stop.

The speed train went through three cars of the passenger train. Fifty-three people were killed and more than 70 people were injured.

Today, the accident, known as the "Terra Cotta" crash, is mostly forgotten.

However, the crash changed railroading, according to Richard Schaffer, a D.C. firefighter who spent 10 years researching the crash. It hastened the conversion of passenger cars from wood to steel and led to improvements in railroad signaling.

In June 2009, a D.C. Metro subway train crashed into another subway train in almost the same spot.

"The irony was it was practically the same location and practically all the same problems, human error, signaling problems, construction quality of the trains," Schaffer said. "If you forget what's happened before you, you don't have a foundation to live upon."

Congressional Cemetery

The Congressional Cemetery is where a majority of Washington's political elite makes their eternal rest. In the 1800s, it was the site of grand funeral processions where tens of thousands of people would gather to watch soldiers carry fallen leaders to their resting place.

"I'm sure there are quite a few secrets buried here," said Abby Johnson, a professor of literature and history at Georgetown University.

There is also a "Public Vault" that is a crypt the size of a one-car garage. It was built in the 1830s to store the bodies of public officials until the ground thawed or they were moved to a different location.

A skeleton key is needed to gain entrance.

The vault was a holding place for Dolly Madison, William Henry Harrison, John Quincy Adams and Zachary Taylor. The president shave all been moved to their home states.

Today the Congressional Cemetery is overshadowed by the better-known Arlington National Cemetery.