Whats a "capitol"?

Answer 1

The United States Capitol is the capitol building that serves as the location for the United States Congress, the legislative branch of the U.S. federal government. It is located in Washington, D.C., on top of Capitol Hill at the east end of the National Mall. Although not in the geographic center of the District of Columbia, the Capitol is the focus by which the quadrants of the district are divided.

The building, designed by William Thornton, is marked by its central dome above a rotunda and two wings, one for each chamber of Congress: the north wing is the Senate chamber and the south wing is the House of Representatives chamber. Above these chambers are galleries where people can watch the Senate and House of Representatives. It is an exemplar of the Neoclassical architecture style.

Construction of the current Capitol building began in 1793. As reported by the Columbian Mirror and Alexandria Gazette on September 23, 1793, George Washington laid the cornerstone on September 18, 1793, in the 13th year of American independence, after a Masonic ceremony;[1] the stone is located near the Old Supreme Court, through a passageway taken by people visiting the United States Senate Gallery. It is not known that this actually is the original cornerstone, but it was engraved with a masonic symbol and commissioned in 1893 (100 years after is placement). The cornerstone has been moved from its original location. The Capitol was built and later expanded in the 1850s using the labor of slaves "who cut the logs, laid the stones and baked the bricks."[2] The original plan was to use workers brought in from Europe; however, there was a poor response to recruitment efforts and African Americans—free and slave—composed the majority of the work force.[3]

Answer 2

capital: a city of government
Example: As the bus approached the capital, the students cheered.

capitol: a building of government
Example: By the time they reached the capitol building, they were ready to go home.

Answer 3

It's a building where a legislature meets.
(Note, it's not a "capital," which would be the seat of government for a nation or state.
"I went to the Capitol building in our nation's capital, Washington D.C.")