History has been full of mysteries. Things that are baffling or hard to explain. While we can rule out silly explanations like Aliens, we sometimes can't come up with a logical answer. There are many explanations for each of these mysteries, but they lack a definitive answer. All of these mysteries are linked to civilizations that existed before the modernity of the world. Some ancient, some not.
http://www.ranker.com/list/10-mysteries-of-pre-modern-civilizations/obsessivelister,
Inca Architecture
The Inca were an advanced civilization. Machu Picchu is their legacy. The bricks they used to create walls and buildings are somewhat baffling. Some bricks are shaped like trapezoids, and each brick perfectly fits into place. So much so, that it's impossible to stick a blade in-between.They also cut and shaped these by using primitive tools like simple rocks. They also lacked mortar. The fact that they built large terraces in order to balance their buildings from falling off the mountain is both baffling and spectacular. Other than their engineering and architectural skills, it's also baffling how they disappeared not too long after building Machu Picchu. It's widely accepted that a smallpox epidemic wiped them out.
Costa Rica Spheres
Expeditions to the Americas
Monoliths
From all over the world there have been civilizations that utilized the use of giant stones. These stones are used to build a wide range of creations. From giant columns, to giant statues. The largest monolith moved from ancient times would be a statue of Ramses II that toppled over in the Ramesseum. Without the use of modern tools like cranes it's hard to imagine how they lifted these objects. It's not impossible for them to have lifted them but even today we are baffled at how exactly they moved them. There are many theories but it's still universally undecided. To understand how it would be possible, look up videos on Wally Washington.
Fall of the Minoan Civilization
Nazca Lines
Engineering the Pyramids
This one ties in with number one. We now know who built the pyramids. It wasn't slaves but workers who were more than likely paid for their services. So we know the answer to that mystery, but how exactly were the pyramids built? There are many different theories on this one. The most logical answer would be that they lubricated the walkway underneath the blocks as they lifted them upwards. Logs, rampways, and ropes are usually tied in to the answers. And yes it was very possible for them to have built it and not aliens.
Mayan Civilization Collapse
Carnac Stones
Lost Roman Legion