Dr. Ivan Šprajc has spent the past 30 years looking for Maya cities in Mexico's Yucatan Peninsula. In 2013, the archeologist and his team found one dating back to the 8th century in the Chactún rainforest. A year later, they unearthed two more cities abandoned over 1,200 years ago. But a massive ancient settlement found deep inside Mexico's Balamkú Ecological Conservation Zone, is the team's most exciting discovery yet.