11 ancient sites that are mysteriously aligned with the sun on the equinox, in photos

From top left clockwise, Teotihuacán in Mexico, Angkor Wat temple in Cambodia, the Great Sphinx and Pyramid of Khafre in Egypt and the Knowth Neolithic passage grave in Ireland.Ronaldo Schemidt/AFP via Getty Images; Cavan Images/Getty images; UniversalImagesGroup / Contributor/Getty Images; oversnap/Getty images

• The spring equinox will take place this year at 17:24 ET on March 20.
• The event marks the start of spring, where day and night are almost equal in length.

There are many reasons to celebrate the spring equinox. For one, it's the time when days start getting longer than nights.

For millennia, people all over the world have marked this mystical occasion, which often symbolizes the beginning of spring or a time of rebirth.

Archaeologists have found many ancient sites that line up with the equinox. But the purpose of these sites often remains shrouded in mystery.

As the spring equinox is around the corner — at 17:24 ET on March 20 — we look at 11 sites that line up with the equinox, and what experts think about them.