The playing surface for baseball. Consists of a diamond shaped "infield" with 4 rubber slab bases, a pitcher's mound in the middle, plus a grassy "outfield" area on the opposite side of the home plate where the batter and catcher stand. Typically features chalk lines drawn between the bases and along the sides.
The infield is commonly, but not required to be, made of dirt. There are two dugouts where the players rest when they're not batting or fielding. The outfield can be any size and ends in a wall or fence.
