GameSpy has put together a two-page preview of the world editor that will be included with THQ and Iron Lore's Titan Quest, after seeing a demonstration of what the editor is capable of. Check it out:
After laying down assorted set pieces to bring the small corner of the world he's created to life, our host determined that the best thing to use to bring his lush little valley to life was a river to run through it. Which -- you guessed it -- prompted him to bust out his "river tool." Following the "painting-on" theme, he proceeded to fill the small valley with a body of moving water, of the proper elevation. "Moving water" being the key: Titan Quest's river tool allows you to set the direction (or directions, depending on whatever bends you decide to carve into your riverbeds) that you want your water to flow. There's also a tool for creating still bodies of water, for use in pools, ponds, and the like.