The Capitoline Grounds, also known as Capitoline Skating Lake and Base Ball Ground, was a baseball park located in Brooklyn, New York from 1864 to 1880. It was built to rival nearby Union Grounds, also in Brooklyn. The park hosted local amateur teams in its early history, but later hosted professional and semi-professional games. The park's only season as the home field for an all-professional team occurred in 1872 when the Brooklyn Atlantics joined the National Association of Professional Base Ball Players. The park was flooded during the winter and used as an ice skating park. The grounds were used by local high schools and colleges as well, to play American football games, and ice rink football matches.
Many of organized baseball's earliest historical events took place at the park throughout the 1860s and early 1870s. The most notable event came on June 14, 1870, when the Atlantics defeated the Cincinnati Red Stockings to end their historic 84-game winning streak. Fred Goldsmith successfully demonstrated his curve ball at the grounds in 1870, a pitch previously thought to have been only an optical illusion. In an 1865 game, Ned Cuthbert is credited with inventing the slide when he tried avoiding a tag when attempting to steal a base against the Athletic of Philadelphia. In addition to baseball, the grounds hosted various events and exhibitions; most notably in 1873, when Washington Donaldson and two reporters attempted to fly a hot-air balloon across the Atlantic Ocean. The attempt turned tragic when the balloon crashed in Connecticut killing one of the reporters.