[20, Clava Cairns, near Inverness, Scotland] These earliest man-made stone structures were for the living and for the dead — most were tombs designed in a way that lined up with the heavens, that seemed to indicate a kind of religion and a concern for the afterlife.

[21, West Kennet Long Barrow, Avebury, England; Lanyon Quoit, Cornwall, England] Long before the pyramids of Egypt, the powerful had stone tombs built to protect their bodies. The soil that buried this structure has long since eroded away.

[22, Newgrange and Knowth passage tombs, County Meath, near Dublin] These ancient peoples' lives were dictated by the seasons and the natural world around them. Again, the greatest tombs aligned with the rising sun.

[22A, Knowth, c. 3200 BC] This is a "necropolis" — a city of the dead — built in Ireland, with several grassy mounds around one grand tomb. Being a passage tomb, it tracked the sun, with one tunnel facing east and one facing west — aligned so that on both the spring and fall equinoxes, rays from the rising and setting sun shine down the passageways, illuminating its central chamber.

[23, Knowth, near Dublin]
Guide: To give you an idea of the sweep of the history here, these sites were built approximately 5,300 years ago — approximately 3300 BC — which puts them 500 years older than the oldest pyramids in Egypt, 1,000 years older than Stonehenge in Wiltshire in England. So these people put a huge amount of energy and resources, and basically a huge amount of their wealth, into constructing these monuments. They were probably thinking not just about survival but issues around life, death, the story of their tribe, their ancestors; issues like rebirth, where did they come from, where were they going to.

[24, Newgrange, c. 3300 BC, near Dublin] Nearby is an even older sacred mound, also built for some kind of ritual of the sun. An impressively large structure faced with white quartz and decorated with abstract engravings, it's a testament to the engineering abilities and desire to ornament of people from over 5,000 years ago.

[25, Newgrange, near Dublin] A narrow passageway leads to the central chamber under a 20-foot-high stone dome. Bones and ashes were placed here under a massive mound of stone and dirt to wait for that special moment when, as the sun rises on the shortest day of the year, a ray of light shines into the passageway and for 17 minutes it lights the center of the sacred chamber.

[26] Perhaps this was the moment when the souls of the dead would be transported to the afterlife via that mysterious ray of life-giving and life-taking sunlight.

[27, Neolithic Age, c. 10,000–3000 BC] Roughly 8,000 years ago, across Europe, the last part of the Stone Age was marked by tribes settling down, shifting from hunter-gatherers to farmers. This was the Late Stone Age — also called the "Neolithic Age" — still before the advent of metal working.

[28, Maeshowe Chambered Tomb, c. 3500 BC, Orkney, Scotland. Guide: Kinlay Frances of Orkney Uncovered, www.orkneyuncovered.co.uk] On the isle of Orkney at the far north of Scotland in what seems like just another field, is a remarkable burial mound, or chambered tomb. For 5,000 years, people have lowered their heads to enter this sacred space.

Rick: Wow! This is great. Tell me about this place.
Guide: This is a burial chamber, and to our right and our left, and behind you, are three tombs. On winter solstice, at sunset, the sun streams through this position here, and illuminates the back chamber.
Rick: Wow!
Guide: The stone is sandstone, and it's been hand-carved and corbelled, vaulted into position, to make this beautiful chamber. And how Neolithic man managed to build this structure, no one really knows.

[29, Skara Brae, Orkney, Scotland, c. 3100 BC] Orkney is dotted with monuments recalling when it was a center of civilization, back in the Stone Age, with more people then than there are on the island today. Imagine a community here, hunkered down in subterranean homes, connected by tunnels.

[30] Guide: It was a big community — 150 people living here at one stage. A third of the village remains. Two-thirds were taken away by the North Atlantic. People lived under the ground, in stone-type igloo buildings with turf roofs, and they lived under the ground to keep the weather out, to keep them warm. They were powered by oil lamps, with whale oil and whalebone basins, and a very nice-looking community.