Pitching Rubber and Mound
In the center of the diamond, one will find a flat piece of rubber atop a mound of dirt. The height of the mound corresponds to the distance of between the bases; for every 10 ft that distance goes down, the pitcher's mound must go down two inches. A diamond with bases that are 90 ft apart has a 10-inch mound, one with 80 ft apart has an 8-inch mound and so on. The rubber itself is 24 inches long and is about 60 feet away from home plate (for a 90 ft field).
The pitcher's mound in baseball is raised area of dirt in the center of the infield containing the pitcher's rubber, from which a pitcher throws. It is called a mound because it is slightly sloped, like a small hill.