Plato indicates that the language of Atlantis was not Greek (Critias 114b), but doesn't appear to say what that language was.
Ah, but the Atlantians didn’t include primers, pictographic instructions, pictographic dictionaries, regular dictionaries, illustrated texts (OK maybe that), tens of thousands of regular text only books, and an audible guide to pronunciation of all the Atlantian phonemes.
Maybe I should add a Rosetta Stone, although I rather doubt any current language would survive a global disaster and 5,000 years in any recognizable form.
What do you think should be included?