The Stonehenge monument in England is known for its alignment with the summer solstice sunrise, and a is popular destination for revelers welcoming the longest day of the year. The inner “horseshoe” of the monument opens toward the point on the horizon where the sun appears on the day in June when the sun’s path is furthest North.

But on the same axis, in the opposite direction, is the point on the horizon where the sun sets on the winter solstice. And some experts suspect that the midwinter alignment may have been the more important occasion for the Neolithic people who built Stonehenge.

John North, a historian of astronomy, wrote in his book Cosmos:

The usual interpretation of Stonehenge would make its center the place from which the midsummer sun was observed over the Heel Stone. This is almost certainly mistaken. The viewing position was at the Heel Stone itself, outside the sacred space, and the chief celebration was that of the setting midwinter Sun, seen through the narrow central corridor. Stonehenge is a skeleton through which light can pass from numerous directions, as in the timber monuments before it, but all of these were carefully planned so as to present a solid appearance against the sky when viewed from suitable positions — and the Heel stone is just such a position. Sight of the last glint of winter sunlight through the center of the black edifice must have been deeply moving.

To learn more about Stonehenge and see us test North’s idea on a model kit of the monument, check out the video above. And for more Vox videos, subscribe to our channel on YouTube.