In the 'Foundation' series, the first Foundation is located on the planet Terminus.
Hari Seldon establishes the Foundation on Terminus at the far edge of the Galactic Empire. Its public mission is to assemble scientists and preserve humanity's accumulated knowledge in the Encyclopedia Galactica as the Empire approaches collapse.
Terminus is deliberately remote, resource-poor, and politically insignificant. That isolation helps protect the Foundation from immediate Imperial interference, while its distance from the galactic center makes it a natural starting point for Seldon's plan to shorten the coming age of barbarism.
A common mix-up is choosing Trantor, the wealthy Imperial capital and Seldon's original home. Anacreon is a neighboring kingdom that later threatens Terminus, while Kalgan becomes important in later conflicts. The First Foundation's homeworld is Terminus; the Second Foundation is associated with a different, concealed location.