The design and construction of public amenities, usually exterior. Roads, bridges and dams being the obvious examples.
Dont forget tunnels -- KarlZdero?
Completely off topic: my favourite part of Ken Burns's documentary on the American Civil War concerned Grant's march. The confederate army sabotaged bridges and rail lines in front of Grant, but Grant marched with a corps of engineers that repaired the works as Grant moved, frustrating the confederate efforts. At one point the confederates collapsed a tunnel, but one confederate soldier complained it wouldn't make a difference, "Grant probably carries a spare tunnel with him."
And them Suth'ners whine about Sherman's march to the sea... :)