Terminus is the sole planet orbiting an isolated star. Its nearest inhabited neighbor is Anacreon, 8 parsecs (26 light years) away, and it lies approximately 10,000 parsecs from the capital of the First Galactic Empire, Trantor, near the galactic center.
There are almost no visible stars in its sky, only the huge lens of the Milky Way Galaxy. The nearby stars of the Province of Anacreon are known as "The Diamonds", with the expanse of the Galaxy described as "The Lens". The Ecliptic plane of Terminus appears to be near-perpendicular to its orbit around the Galactic nucleus, as the Lens is visible in the night sky throughout its year, while the Diamonds appearance appears to be seasonal. The visibility of the Magellanic Clouds is not discussed.
Terminus has a very high water/land ratio, with the capital, Terminus City, situated on the planet's only truly large island (not quite a continent). The planetary ocean contains a total of approximately 10,000 inhabited islands. In this way, Terminus resembles the Japanese Archipelago, culturally as well as in terms of technological prowess (see below).
Terminus's climate is mild. Like all known habitable planets it has a nickel-iron core which produces a significant magnetic field; however, it has almost no metals in its surface rocks. In the Foundation's early years, steel was so valuable that it was used to coin money.
Prior to human occupation, a few lower forms of life existed on Terminus. However, once humans arrived (along with their supporting species), these native life forms were crowded out and became extinct in the wild. However, breeding populations were conserved at various Universities.
The capital of Terminus Planet is Terminus City. Terminus City is home to a number of noteworthy places, including:City Hall—the primary administrative building of the Foundation (and later the Foundation Federation), including the Council Chambers and Mayor's Office
City Hall Park
The Hardin Building—a public apartment complex
Mallow Hall—a concert venue
The Salvor Hardin Museum of Origins—more commonly called the Hardin Museum, a museum of Foundation history, known to house the copies of the original Encyclopedia Galactica
The Seldon Vault—where messages recorded by Hari Seldon before his death were played to relay important information to the citizens of the Foundation, around the times of the Seldon Crises.
Three other cities are known: Agyropol, Newton City, Stanmark (Arkady Darrell's hometown).
With the Galactic Empire in fatal decline, Hari Seldon, inventor of the science of psychohistory, predicted a 30,000 year interregnum of barbaric Dark Ages until the rise of a New Empire. So Seldon created a plan to shorten this interregnum from 30,000 years to 1,000 years.
Seldon asked Las Zenow, chief librarian of the Library of Trantor to undertake a search to find a suitable planet, according to Seldon's criteria. Zenow, following a lengthy search, found Terminus, which had been uninhabited through the five centuries after its discovery.
Seldon manipulated the authoritarian Commission of Public Safety that ruled the Empire to exile his project to Terminus. The founding population consisted of 100,000 especially healthy scientists, whose ostensible purpose was to publish an Encyclopedia Galactica. In actuality, their job would be to preserve science and technology, and to reconquer the Galaxy to form the Second Empire.
The lack of steel and limited natural resources forced Terminians to develop technologies of extremely high efficiency, as their knowledge due to their position as the inheritors of the Imperial Library allowed them to do so. The high technology and science of the foundation became its crucial strength in early confrontations, first against far larger local kingdoms that had broken away from the weakening empire but drastically regressed to pre-atomic technology. And later, against powerful dictators with support from the dying core of the Empire itself, who had similar scientific ability to the Foundation but far more cumbersome, inefficient technology, having always relied on colossal resources.
Economically, at least for the first 500 years, they seem to have a massive surplus in labor. Toran Darrell II and Janov Pelorat were both described as men of modest means, one living off a stipend, the other a quiet academic in an unpopular field. Yet both men were able to afford a house servant (Poli for the Darrell household and Kloda for the Pelorat household). Poli in particular is shown at length to be very under-educated, speaking in a fashion that seems indicative of the antebellum South. Whether this is due to her inherent limits, a bizarre affectation or a lack of educational opportunities on Terminus is not explained. The labor saving devices as described would seem to be the equal or more of 20th century gadgets, and what the servants are supposed to do is not explained, though it describes them doing menial tasks such as setting out pre-made self-cooking dinners or opening doors.
In the later Foundation books, primarily Foundation's Edge and Foundation and Earth, Terminus is well on its way to being the capital of the Second Galactic Empire, using its massive technological advantage. This even threw a wrench into the plan of the Second Foundation, as Terminus had managed to develop anti-mentalic technology, including a psychic barrier, which was strong enough to hold off at least temporarily Stor Gendibal's mentalic power, and with Gaia's help (had Golan Trevize chosen it) would have been indestructible to mental attacks.