The architects who won the 1802 design competition, are a true testament to New York City's multiculturalism: U.S. architect John McComb, Jr., and freed slave Joseph-François Mangin (some accounts say he was born in Haiti, others France). Mangin, who designed St. Patrick's Old Cathedral on Mulberry Street, and McComb, who designed Castle Clinton, were jointly awarded a prize of $350.
Under construction from 1803 to 1812 (delayed due to City Council's objection that the design was excessive), it was built in a Federalist style, emulating much of what was being built in Paris at that time.
New York City Hall is listed as a National Historic Landmark, and is on the National Register of Historic Places, with landmark designation in 1966 for its exterior, and again in 1976 for the interior.
Before ascending the steps to enter, there is a large plaque on the ground, which commemorates the first excavations for the city's subway system.
After entering, one will notice the amazing American-Georgian interior design of marble, sandstone, limestone, and painted wood...
...which leads to one of the United States' largest floating marble stairways.
Before heading up the stairs to the second floor, take a look up to see the rotunda's dome.
Sadly, it is the second dome, as the first burned down during a 1858 firework show for the celebration of the laying of the Transatlantic cable. The copper statue of Justice, atop the outside of the dome, is also a replica of the first that came crashing down with the dome, and, strangely, is one of the few in the U.S. to not be blindfolded.
Most rooms within the Hall are not locked, except for one, the Governor's Room, which is normally opened only for tours, or special guests.
The room holds a large portion of the of the building's oil portrait collection (which is estimated to be worth a total of $100 million), as well as George Washington's desk (seen below at the center of the room).
Also, if one feels politically motivated, you may take part in Council meetings in the Hall's Council Chambers.
One may attend Committee, and Stated Meetings to voice your opinion on public matters, which are held twice a month, and are a proud distinction to our admirable democracy. A full listing of public meetings is available at this link.
On a morbid side note, this room's balcony was also the scene of a murder.
While New York City Hall briefly held the bodies of Abraham Lincoln, as well as Ulysses S. Grant, and Colonel Elmer Ephraim Ellsworth (the first Union officer killed in the Civil War), the first to lay in state, due to political assassination within the grounds, was Brooklyn Councilman James E. Davis. In 2003, Othniel B. Askew shot and killed Davis on the balcony of the Council Chamber. A plainclothes policeman, Richard Burt, then shot Askew from the ground floor, hitting him five times, and he later died at Beekman Downtown Hospital.
Anyhow, whether you visit to let your civic voice be heard, or just to see a piece if this city's history, I highly recommend it, and there are groups (such as New York Adventure Club - link here), that hold after-hours tours of the building.