Arcadia (planet)

Arcadia was the name of at least one place, but plausibly more than one place, in the universe.

According to one account, it was planet on which a Human colony was established in the 26th century. The Doctor visited Arcadia and found it to be a non-technological paradise which served as a living specimen for a centuries-long experiment. (NA: Deceit)

Other references to Arcadia were considerably more vague, and failed to go so far as to call it a planet. It was possible that these additional references considered a city, planet, system, or empire, which may have been different from the 26th century Human colony of the same name. The principal fact known about Arcadia from these sources was that it was the site of a major event in the Last Great Time War. The Doctor once mentioned that he was present at the Fall of Arcadia during that war, and that he still hadn't gotten over its fall. (DW: Doomsday) Later, the Eleventh Doctor took Amy Pond to Arcadia, suggesting that it was not entirely time-locked like other parts of the Time War. Her comment to the Doctor that he was being exceptionally nice to her by taking her to Arcadia suggested that it was a pleasant place, at least when they visited it. (DW: Vincent and the Doctor)

Provided that the reference was to the Arcadia of the Time War, the only specific fact known about Arcadia was that its diamonds were very valuable. (TW: Kiss Kiss, Bang Bang)