Secrets you probably didn't know about 7 famous landmarks in Washington, DC

• Washington, DC is home to America's most historical landmarks.
• These landmarks attract thousands of visitors, but also have secrets and interesting backstories.
• A hidden crypt, a "whispering gallery," and moon rocks can be found in DC.
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Following is a transcript of the video.

1. The Lincoln Memorial had a typo.

In the inscription of Abraham Lincoln's second inaugural address, the word "future" started with an E instead of an F. The bottom part of the E was filled in to fix it. But if you look closely, the extra leg is still visible.

2. The Washington National Cathedral has a 3.6-billion-year-old piece of space.

This is the cathedral's Space Window. Right in the center is a sliver of moon rock that's 3.6 billion years old. The cathedral received the moon rock from Apollo 11 astronauts Neil Armstrong, Buzz Aldrin, and Michael Collins in 1974.

3. The Washington Monument wasn't meant to be 2 colors.

Construction began in 1848. It was built with marble, blue gneiss, and granite. Six years later, the Washington National Monument Society ran out of money, and construction stopped for the next 25 years. In 1876, the US government took over the construction. Marble from a different quarry was used to finish the monument. Over time, each section changed color based on how the materials reacted to the weather.

4. The White House and the Capitol were designed through a public competition.

George Washington, Thomas Jefferson, and the commissioners of DC judged the competition. Jefferson submitted drawings for the White House design himself, but Irish architect James Hoban won the commission. The Capitol was designed by physician William Thornton. He won the competition with no formal training in architecture.

5. The Thomas Jefferson Memorial was originally a monument site for Theodore Roosevelt.

A Theodore Roosevelt monument was planned in the 1920s, but Congress never gave it funding. After he was elected in the 1930s, Franklin Roosevelt pushed to get a memorial for Jefferson. Congress created the Thomas Jefferson Memorial Commission. Architect John Russell Pope designed the memorial, and Pope used Jefferson's architectural styles in its design.

6. There's a "whispering gallery" in the Capitol.

In some areas of the National Statuary Hall, you can whisper and still be clearly heard yards away. The hall is one of the most popular rooms for tourists today.

7. The Capitol was meant to be George Washington's burial ground.

After Washington's death in 1799, Congress wanted to honor him. The chamber in the Capitol was still under construction. So Washington was placed in a temporary tomb at Mount Vernon in Virginia. But he requested in his will that he be buried in his home of Virginia, so his body stayed at Mount Vernon.