It was to be made of wood and supported on stone towers called piers which were to stand in the river. ... The finished road stood over sixty feet above the river. For major or busy bridges sometimes stone went in place of wood. ... Sometimes a route of an aqueduct required that a short tunnel be dug through a hill. ... The Romans achieved this feat through the use of the keystone block. ...

• Word Count: 1593
• Approx Pages: 6
• Grade Level: High School