Asgard is a small other dimensional planetary body (its surface area being about the same as that of the continental United States), whose nature and physics are different from those of planetary bodies in the Earthly dimension. Asgard is not a sphere like the Earth of Moon, but a relatively flat asteroid-like landmass suspended in space. Asgard does not rotate about its axis, nor does it revolve around a sun. Asgard has intervals of night ad day (of undisclosed durations) even though it does not rotate. There is no evidence of changing seasons, however. It is not known if Asgard's source of light and heat is the Earth's sun, a sun in the Asgardian dimension whose gravity does not exert itself on Asgard, or a glowing ball of light dissimilar to a star in most of its properties. Unlike Earth, Where the force of gravitation radiates from the center of the sphere, Asgard's gravity apparently radiates from some point or object beneath the suspended landmass. Consequently, there is a top side to Asgard, upon which beings can stand, and a bottom side where beings cannot stand and from which they will fall through space toward the source of gravitation. At the boundaries of Asgard's landmass, a being or object can step off into the void.

There is apparently some force that keeps the bottom and edges of Asgard's landmass from eroding away. Whatever this force is also prevent the bodies of water which are at certain of Asgard's boundaries from pouring off into the void, as well as preventing Asgard's atmosphere from escaping, Asgard has been described as floating on a "Sea of Space." This sea apparently has a surface, one that is navigable by certain Asgardian ships that resemble Viking longboats. The exact nature of space in the Asgardian dimension is unknown.

While the gravity of Asgard is roughly analogous to Earth's, common matter is considerably denser on an average. Consequently a chair made of Asdardian wood would be more massive (and heavier) than a chair made of analogous Earthly wood. Rocks, water, flesh, bone, steel - all matter is denser and thus more durable.

Besides all of the anomalies described above, Asgard is connected in some as yet unknown way with at least two other dimensional planes, one of which is that of the Earth (whom the Asgardians call Midgard, a word meaning "Middle Realm"). The Asgardians refer to all of the major known inhabited realms of their cosmology as the "Nine Worlds." Only four of the Nine Worlds are located on the main Asgardian landmass: Asgard, home of the Gods, Vanahelm, home of the Asgardians' sister race, the Vanir, Nidavellir, home of the Dwarves, and Alfheim, home of the Light Elves.

The remainder of the Nine Worlds are on separated landmass isolated from one another by interdimensional space. Midgard, our Earth, does not appear to be physically affected by the motions of any of the other physical bodies in the Asgardian cosmology, although Earth's axis (the imaginary pole around which it rotates) is in alignment with one of the roots of Yggdrasil, the cosmic ash tree that stands in Asgard. Jotunheim, the world of the giants, is a flat ring-shaped realm with high mountains along its inner edge. It is apparently on its own separate dimension plain, discrete from Asgard's and Earths, home of the Dark Elves, is another asteroid-like land-mass, smaller than Asgard. There are numerous nexus-portals between the mountains of Jotunheim and Svartalfheim and the mountains of Asgard permitting easy passage by denizens of each realm. These passageways make Jotunheim and Svartalfheim seem like "underworlds" of the Asgardian continent itself.

The eighth of the Nine Worlds is Hel, realm of the dead, and its sister realm, Niffleheim. In the Asgardian scheme of afterlife, the heroes and honored dead go to Valhalla, a special region of Asgard, the common dead go to Hel, and the dishonored dead (murderers and other evildoers) go to Nefflehelm, and Valhalla possess the necessary physical conditions to permit the astral form of the deceased to exist there for indefinite periods of time. At one time, Hela, goddess of the dead, usurped the rule of Valhalla, despite the fact it was on a different dimensional plane than Hel. Odin has since reclaimed the land. The ninth of the Nine Worlds is Muspelheim, land of the fiery demons. Until his recent disappearance, the primordial demon Surter ruled Muspelheim. Muspelheim is on its own dimension plane, separate from from all the other Nine Worlds.

In the Asgardians account of the origin of their cosmology, Muspelheim, the land of fire, and Nifleheim, the land of ice, were said to predate recorded time, separated from one another by Ginnungagap, the Yawning Void. Asgard is honeycombed with nexus-portals to the various extradimensional realms or the Nine Worlds, making the worlds (with the exception of Earth) sometimes seem like they are on a contiguous plain. (Indeed, early cartographers of Asgard mapped it this way.) The only permanent portal to Earth, Bifrost, the Rainbow Bridge, has recently been shattered, severing Asgard's connection with Earth and making passage between realms difficult. There is a special passageway from Asgard to the extradimensional realm of Olympus, home of the Greek gods. Since Olympus is not part of the Asgardian cosmology, this nexus-portal is believed to be an artificial rather than natural phenomenon.

It is possible that somewhere in Asgard's outlaying Sea of Space there are floating nexus-portals to Earth's space. Beings of the Earthly dimension have in certain instances been able to travel from Earthly to Asgardian space. There may indeed be an edge to Asgard's Sea of Space, perhaps at the perimeter of the "Dome of the Sky" extending from the outer edge of ringed Jotunhelm. At the edge of the Sea there would exist "dimensional borderlands" which serves as transitional areas between discrete dimensions. Asgard and its sister realms are populated by six distinct humanoid races, described under Asgardians. Besides these, there are several singular cratures who exist upon various of the Nine Worlds.