Garrison
An Adventure map object used for storing armies. Enemy heroes can't pass the garrison without fighting the armies stationed inside. Garrisons can be aligned both horizontally and vertically. Since the creatures left there have neither the benefit of a hero leading them nor the defensive structures of a Town with a Fort built in it, this manouever tends to be not of much use.
Warning: Mapmakers may set up a garrison so that the units stationed inside cannot leave. Make sure that isn't the case before storing in a garrison anything you might want to use later on.