( CNN ) A sweat-smothered man in a wide-brimmed hat , knee-high leather boots and a khaki uniform machetes his way through lush jungle foliage . As thick tangles of vine fall beneath his blade , he pushes into a clearing , then suddenly staggers back . The fanged mouth of a primordial stone beast gapes toward him . Before him rise the crumbled ruins of an enormous portal of rock , black with age but with a colossal grandeur not yet lost -- a fine example of what archaeologists call a `` zoomorphic portal '' or , more popularly , a `` monster mouth gate . '' What was once the gateway to an ancient Mayan city , built circa 700 AD and mysteriously abandoned four centuries later , stands before him . He has found the lost city of Lagunita . Now that the planet has been mapped , circumnavigated , measured and tagged in every way imaginable , the age of explorers discovering new worlds seems a quaint memory . But there are still adventurers exploring forgotten corners of the globe , and some find astonishing things . One such explorer , part Indiana Jones , part Magellan , is Slovenian archaeologist Ivan Šprajc . The sprightly Šprajc wears the weathered face of a man who has spent much of his 60 years beneath a hot sun at excavations , or hacking his way through dense jungle . He has been the first to see ancient pyramids , 30 meters high , that he spotted in aerial photographs from his office among the Baroque Mitteleuropean cobbled streets of Ljubljana , Slovenia , some 10,000 kilometers away . But in terms of the thrill of discovery , it does n't get any better than his encounter with Lagunita 's monster portal . What does it feel like to find a lost city ? `` It 's a victory , '' says Šprajc , `` especially when the efforts are long . On several occasions we 've had two , three weeks of just cutting through the bush to get to some location , without knowing what we would find . When we get to the site it feels like a big victory , like we 've done it . If it had been easy , then other people would have done it already . '' Since 1996 , he and his team have discovered more than 80 ancient Mayan cities in the jungles of Mexico , few of which the modern world had known before . But how can an entire city , which once may have been home to tens of thousands , simply vanish ? Šprajc explains that the region in which he has found such riches had gone unexplored because it 's so inaccessible : `` It 's so hard to get there . It 's a biosphere , a protected natural area that has never been densely populated since the collapse of the Classical Mayans , for the past thousand years or so . '' When a primal jungle is allowed to grow rampant for centuries , it can indeed swallow entire cities . But just why so many settlements were simply abandoned , long before the arrival of the Spanish conquistadors , remains a mystery to which these long lost sites may provide an answer . `` Ninety-nine percent of settlements in the central and southern lowlands of the Yucatan peninsula were abandoned in a matter of 200 years . By 1000 AD , practically everything was abandoned . That was the situation when the Spaniards came . But not so in the northern section of the peninsula and the Guatemala highlands , where there was no rupture until the arrival of the Spaniards . '' So what happened in that enormous area that led to this mass evacuation ? `` Nobody knows the exact sequence of events , but it was definitely a combination of droughts , climate change , ( and ) overpopulation , but other things must have come as consequences : devastating raids and wars among the Mayan states , which resembled the constantly battling ancient Greek city-states . `` In this Late Classical period , wars intensified with devastating consequences , for if one city-state was destroyed or overcome , it had a ripple effect on trade networks . It was a sort of globalized Mayan world . '' To learn more would require extensive , time-consuming surveys of each site , which is a different sort of fieldwork than Šprajc likes to practice . His team will map what appears to be the core of a settlement , but there simply is n't time or manpower to map it all , so hundreds of structures are left for others to survey and excavate . The adrenaline of the treasure hunt is what drives Šprajc , the `` Eureka '' moment when he finds the buried treasure . He is not in the least proprietary about what he discovers , preferring to let other research teams dive in to the sites he has found to slowly excavate , catalogue and analyze what he finds . `` [ This extensive mapping ] is not our job . We are taking the first step into an unknown area . '' Šprajc is a throwback to the great 19th century explorers -- a dying breed as the world becomes smaller and science bleaches out its mysteries . But in the heat of the jungle , science can only get you so far . Intrepid spirit , calloused palms , sweat , blood and patience are more important than gadgetry . As Šprajc likes to say , `` We can survive without computers , but not without machetes . '' Noah Charney is a professor of art history and best-selling author . He teaches a Guardian Masterclass called `` How to write about art . ''
Slovenian archaeologist mark Šprajc discovers ancient Mayan settlements in the vicinity of Mexico . His findings can help explain why so many Mayan cities were abandoned before the arrival of the explorers .