- "The nearest telephone is light-years away. This is another world, a closed universe. It's not quite like Earth, I mean, this place is filled with dinosaurs and monkey-like people that we call Pakuni, and... in fact it was built by the ancestors of some giant insect-like creatures that we call Sleestaks [sic].""
- ―Rick Marshall, in s01e16 "Hurricane"
The Land of the Lost is the nickname given to a seemingly artificially-constructed pocket universe visited by Rick Marshall and his children Will and Holly; and later by his brother Jack. The Land is a closed system, which takes the appearance of a planetary surface, orbiting a sun and orbited by three moons. However, it has a somewhat limited surface area, in which one can easily walk away and return to the point of origin without necessarily walking in circles.
Its origins are enclosed in mystery, but it's believed to have been built by the ancient Altrusian race, which created advanced crystal-based technology to control everything from the opening of dimensional portals to the weather of the Land, as well as the intensity of its sun, the movement of the moons and the rotation period around the sun, among other things. These control panels are located within mysterious artifacts known as Pylons, which are bigger on the inside that the outside, much like a Time Lord's TARDIS.
Currently, the Altrusians are gone, their ruined cities populated by their superstitious and savage descendants known as the Sleestak. The Land itself appears like a prehistoric scenery dominated by reptilian creatures closely resembling the dinosaurs of Earth's past, including tyrannosaurs, allosaurs, ceratopsians, sauropods, coelophysis and pterosaurs. Other native forms of life include colorful pig-like mammals, oversized but otherwise Earth-like vegetables, and creatures closely resembling earthly birds, lizards and insects as well as plants.
However the land is also inhabited by stranger forms such as fire-breathing dimetrodont-like beasts, two-headed lake monsters, Yeti-like creatures and the intelligent ape-like Pakuni with their scattered tribal societies; apart from the Sleestak themselves and a form of lepidopteranoid known as the Altrusian Moth. The origins of all these life forms are poorly known: whether they were intentionally brought in or bred by the Altrusians, or entered the Land the same way the Marshall family did, by falling through spacetime doorways.
At one point amidst the forests there is a circular feature on the ground which when opened leads to the core of the Land, an energy generator which appears as a large red crystal floating in an endless void, disintegrating any matter that falls in. This is speculated to be the main source of energy for the Land, the Pylons and the crystals.
- There are numerous aspects about the Land of the Lost world that remain unexplained. While it's generally accepted that the Land realm was built by the Altrusians, and the whole dimensional traveling technology developed by them as well; the exact nature of the mysterious figure called Blandings - a seemingly human being with reality-altering powers seen in the episode "The Repairman" - and hints of a larger power he responds to, are left completely unexplained. So is the nature of the enigmatic entity responsible for the creation of the non-Altrusian temple, which appears in "The Musician".