The first European to travel the length of the Amazon River was Francisco de Orellana in 1542. The BBC's "Unnatural Histories" presents evidence that Orellana, rather than exaggerating his claims as previously thought, was correct in his observations that a complex civilization was flourishing along the Amazon in the 1540s. It is believed that civilization was later devastated by the spread of diseases from Europe, such as smallpox. This civilization was investigated by the British explorer Percy Fawcett in the early twentieth century. The results of his expeditions were inconclusive and he disappeared mysteriously on his last trip. His name for this lost civilization was the City of Z.