Incredible.
The Maya built dozens of cities on the Yucatan Peninsula containing impressive pyramids and temples. The bulk of the architecture was constructed during their classical period, which lasted for several centuries and ended about 1000 years ago. After that, the Mayan people started to abandon metropolitan areas in favor of smaller nomadic communities. By the time the Spanish Conquistadors arrived in the 1500s, all urban settlements were mostly in ruins and reclaimed by the jungle.
This book focuses on two men, Stephens (an American) and Catherwood (an Englishman), who began exploring the ruins in 1840. Prior to that, essentially nothing was known about this lost civilization. Even today, much is speculated, and archaeological sites are still being unearthed.