For a more tangible look at the spiritual mystery of this countryside, prehistoric stone circles are scattered all across Britain. These circles — many as old as Egypt’s pyramids — were sacred centers of ritual and worship. They functioned as celestial calendars. Five thousand years ago locals could tell when to plant — and when to party — according to where the sun rose and where the sun set. It still works that way today.

At the Avebury stone circle, you’re free to wander among 100 stones. Visitors ponder the cohesive ensemble of ditches, mounds, and megaliths — the work of people clearly on a mission from thousands of years ago. The huge circle — while cut in two by a busy road and so big it contains a village — retains its allure and wonder.

And nearby stands Silbury Hill, a yet-to-be-explained man-made mountain of chalk. More than 4,000 years old, this largest man-made construction from prehistoric Europe is just another edifice from England’s mysterious and ancient religious landscape.

And exactly what's it all mean? We’ll never know for sure. It’s like looking at the ruins of a medieval church and from that alone trying to understand Christianity.

Stonehenge is the most famous of Britain’s stone circles. A visit starts at the museum, where you’ll see artifacts from the Stone Age people who built it. A 360-degree theater demonstrates how the structure is aligned with the heavens — marking both the longest and the shortest days of the year. And outside, a thatched-hut hamlet helps you imagine how its Neolithic builders lived.

Huge stones like this replica were quarried, carved, and then moved from many miles — some of them from as far away as Wales, 200 miles to the west. They barged them down rivers; they may have rolled them on logs like this — nobody knows for sure.

After this introduction, a bus shuttles you to the site.

Visitors are in awe as they ponder the continuously debated purposes and meaning of Stonehenge. The major stones were erected at the end of the Stone Age, just before the advent of metal tools. It’s amazing to think that some of these cross stones have been in place for 4,500 years.

Whatever its original purpose, Stonehenge still functions as a celestial calendar. Even in modern times, the sun rises on the longest day of the year in just the right spot, and it retains its powerful sense of wonder over those who gather. For over 4,000 years in a row, this ensemble of stones, so artfully assembled, has silently done its duty.