Otia Imperialia ("Recreation for an Emperor") is an early 13th-century encyclopedic work, the best known work of Gervase of Tilbury. It is an example of Speculum literature. Also known as the "Book of Marvels", it primarily concerns the three fields of history, geography, and physics, but its credibility has been questioned by numerous scholars including philosopher Gottfried Leibniz, who was alerted to the fact that it contains many mythological stories. Its manner of writing is perhaps because the work was written to provide entertainment to Otto IV, Holy Roman Emperor. However, many scholars consider it a very important work in that it "recognizes the correctness of the papal claims in the conflict between Church and Empire." It was written between 1210 and 1214, although some give the dates as between 1209 and 1214 and numerous authors state it was published c.1211.