Presumably the final resting place of Athena, Lord of Kobol after her grief-stricken plunge from the Gates of Hera. It is unclear who interred her, since this took place after the exodus of the thirteen tribes from Kobol. The tomb is located a few days hike from the Galleon Meadow and, according to scriptures, could only be opened with the Arrow of Apollo.
This was not exactly the case - the exterior door to the tomb could be opened by brute force, but the Arrow was required to activate the map therein. The tomb contained twelve stone slabs arranged in a circle, upon or around each of which lay the broken remains of a statue representing one of the Twelve Colonies - Picon was represented by a fish; Caprica, a goat; Sagittaron, an archer; etc.
Kara Thrace placed the Arrow in the bow of the Archer of Sagittaron. Immediately the Tomb's entrance closed, leaving those in the Tomb in darkness. After a few seconds, they found themselves in a grassy field at nighttime surrounded by twelve megalithic slabs similar to those of Stonehenge, either physically transported or immersed in a very sophisticated hologram. On each column was the ancient symbol of a Colony as used on their respective old Colonial flags. Roslin noted that the symbols were used back when the ancient names of the Colonies were used: Aries and not Aerelon, Taurus and not Tauron, Gemini instead of Gemenon, etc.
Above the group, the night sky showed a representation of the same symbol in the form of its constellation as it would be seen on Earth. In fact, Thrace realized that, according to the Scriptures, that they were all standing on a representation of Earth, seeing what their comrades on Earth would see. The map information would be incomplete without one more stellar reference point noticed by Lee Adama in the Scorpius constellation: the Lagoon Nebula, an object visible on Earth and known as well to the Twelve Colonies. Lee Adama deduced that as they approached this point, the ship would be able to further define their position to Earth. Commander Adama noted that the nebula was "a long way away from here." (Home, Part II).
The group was not shown leaving the hologram or the Tomb. It can presumed that the group walked beyond the stones and the image faded to their actual location in the Tomb, then reopened the entrance - either by forcing it open once again or retrieving the Arrow - and exited.
Notes[edit]
Adama notes that the Lagoon Nebula was known to the Colonials by the "astro-number" M8. This is identical to what we call the object on earth according to the Messier catalogue, devised in 1774 by astronomer Charles Messier. The nebula, in reality, appears as a gray object in the sky with binoculars or telescope. It would not be as vivid or large in the sky by the naked eye as it was shown in the group's vision. The object is in the constellation of Sagittarius, not Scorpius, and is 5,200 light years from Earth.
It is acknowledged in the podcast of Home, Part II that the twelve constellations of the Zodiac are never actually all visible at once in the night sky, but rather rotate around the north star throughout the night. The constellations were displayed as in the episode for dramatic purposes.