The Voynich Manuscript is probably the most famous untranslated document in the world, containing 240 pages of text written in an unknown script, embellished with fantastic illustrations of plants, astrological diagrams, and nude female figures. It came into the public eye in 1912 when it was discovered by a Polish book dealer named Wilfrid Voynich.

 

The Manuscript was once owned by Rudolf II, Holy Roman Emperor and King of Bavaria, in the early 1600's, after which it passed through a series of owners, before being forgotten in the library of the Collegio Romano for many years, until being discovered by Voynich and brought into the public eye. Originally it was suspected to be a modern hoax, but the vellum pages have since been carbon-dated to the early 15th century (1404–1438).

 

The text comprises about 35,000 words written in an script sometimes referred to as "Voynichese". All attempts at decipherment have eluded the world's cryptography experts, causing many to think that the text is gibberish, yet linguistic analysis has revealed many similarities with other written languages.

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Source: Wikipedia