We are accustomed to thinking about time in terms of hours, days and years. We remember birthdays, anniversaries and seasons. We think about what happened last week, what we might do next month, perhaps what we hope to achieve over the next few years.

But standing beside a Neolithic monument can stretch the imagination in a completely different direction. Suddenly, fifty years seems very small. A hundred years is barely a moment. A thousand years feels strangely close.