Diodorus Siculus (; Greek: Δι?δωρος Σικελι?τηςDiodoros Sikeliotes) or Diodorus of Sicily was a Greekhistorian. He is known for writing the monumental universal historyBibliotheca historica, much of which survives, between 60 and 30 BC. It is arranged in three parts. The first covers mythic history up to the destruction of Troy, arranged geographically, describing regions around the world from Egypt, India and Arabia to Greece and Europe. The second covers the Trojan War to the death of Alexander the Great. The third covers the period to about 60BC. The title Bibliotheca, meaning ‘library’, acknowledges that he was drawing on the work of many other authors.
I’ve found a passage in Diodorus Siculus’ Library of History that describes a large land mass beyond the Pillars of Heracles that could be ancient Atlantis or America. Here is what he said:
For there lies out in the deep off Libya an island of considerable size, and situated as it is in the ocean it is distant form Libya a voyage of a number of days to the west. Its land is fruitful, much of it being mountainous and not a little being a level plain of suprassing beauty. Through it flow navigable rivers which are used for irrigation, and the island contains many parks planted with trees of every variety and gardens in great multitudes which are traversd by streams of sweet water; on it also are private villas of costly construction, and throughout the gardens banqueting houses have been construcred in a setting of flowers, and in them the inhabitants pass their time during the summer season, since the land supplies in abundance everything which contributes to enjoyment and luxury.
And, speaking generally, the climate of this island is so altogether mild that it produces in abundance the fruits of the trees and the other seasonal fruits for the larger part of the year, so that it would appear that the island, because of its exceptional felicity, were a dwelling-place of a race of gods and not of men. - Diodorus Siculus, The Library of History Book 3, pages 145-146.
I don’t believe this describe ancient America. I believe it describes an ancient memory of Atlantis.