Roman military engineering took both routine and extraordinary forms, the former a proactive part of standard military procedure, and the latter of an extraordinary or reactionary nature. Proactive military engineering took the form of the regular construction of fortified camps, in road-building, and the construction of siege engines. The knowledge and experience learned through such routine engineering lent itself readily to any extraordinary engineering projects required by the army, such as the circumvallations constructed at Alesia and the earthen ramp constructed at Masada.