From his tower Himinbjorg (Ward of Heaven), which sits on the highest point of Bifrost, he guards the bridge. He can see a hundred leagues by day or night, can hear grass growing, and sleeps very little. He is also called Gullintani (Golden Teeth).
The southern span of Bifrost reaches to Midgard. The bridge is built of air and water with protecting fire on it's edges. Everyday the Gods ride their horses and chariots across the bridge to the lower world Thingstead. Thor, however, has to walk his thunder chariot across as it could destroy Bifrost.
May Shining Heimdall bless,