Remarkable feats of engineering from our ancient past span the globe. Some are amazing in size. Others in sophistication. Some are so strange they border on inexplicable. Did the ancients have advanced scientific knowledge that has been lost to time? How--and why--did they fashion these incredible wonders?

The Final Frontier and the ultimate mystery. Scientists are involved in a never-ending quest to understand the vast universe our planet inhabits. But it seems that for each answer science provides, even more questions arise. Our own solar system is populated by mysterious objects and phenomenon that seem to defy our attempts to understand them. And when we get deeper into space, the mysteries only deepen. What could lay beyond the confines of the Milky Way? Are there galaxies similar to our own? Could they be capable of sustaining intelligent life? And is that life trying to contact us?