Position object

From AgeofWiki

Position object is used to move units, buildings, and scenario objects to different parts of a scenario.

How to Use It

Click on the Objects menu, then click on Position Object. Select the unit you wish to move. Click and drag the unit to where you want it to be, then release the mouse button.

To rotate a unit, use the mouse's scroll button, or press Ctrl + Left/Right.

To slightly move the unit's position, use the arrow keys on your keyboard.

Ways To Use it Further

Land and Water Units in Water and Land

Using position object, you can move anything anywhere. For example, you could move houses into a river, or a ship onto a hill.

You can even move buildings inside each other, which is called Building Overlapping.

Advanced Rotation

Using a mod (http://aoe3.heavengames.com/downloads/showfile.php?fileid=187) made by Kast0r, you can even pitch units up and down, which can create some nice effects in your scenario.

An example: