11 ancient sites connected to the spring equinox

El Castillo (The Pyramid of Kukulkan) is a massive Mayan masterpiece that rises above the grounds of Chichén Itzá in the Yucatan jungle. During the spring and fall equinoxes, a shadow slithers along an edge of the 79-foot-tall structure and creates the 120-foot-long body of a snake whose head is carved in stone at the bottom. It’s believed that this display is in honor of the feathered serpent god Kukulkán, who would grant its worshippers health and good harvest. 

For most of the year, visitors are not allowed to enter the inner grounds of Stonehenge in order to protect it. However, four times a year on equinoxes and solstices visitors are allowed to enter the stone circle. A celebration was scheduled for March 20, 2020, but due to concerns over COVID-19, Stonehenge is closed to the public. 

Machu Picchu’s Intihuatana stone was carved so precisely by the Inca that it casts no shadow at noon on the equinoxes. Its name translates to “the hitching post of the sun,” and it’s believed that priests symbolically “stopped” the sun with a ceremonial cord tied around the stone to ensure a good harvest.

Chaco Canyon National Historical Park in New Mexico’s remote Four Corners region is a collection of massive structures dating to 850 CE that’s considered to be the religious and governmental center of the Ancestral Puebloan world. 

Several of the buildings have been determined to mark significant astronomical events, including Casa Rinconada. On the spring equinox, the sun shines through two aligned doorways and into a small niche in the wall. 

Spiro Mounds Archaeological Center is an 80-acre site in rural Oklahoma that was a major political and religious center for the Northern Caddoan Mississippian people between 700 and 1500 CE near the Arkansas River. 

Large earthen mounds were burial chambers for those of high status, with remains and artifacts recovered during the 1930s excavations. On the spring equinox, the sun rises directly behind Mound No. 2 when standing at the main temple. 

Built in the 12th century as a Hindu temple city and later dedicated to Buddhism, Angkor Wat temple complex is the world’s largest religious complex at 402 acres. At dawn, the sun rises directly behind its 65-meter center tower and casts the entire temple in silhouette against the lightening sky.

Mnajdra, a megalithic temple built circa 3600 BCE, sees the morning sun of the spring equinox shine directly through the main entrance down the length of the site and into a recessed shrine. This happens during the fall equinox as well, with sunlight during the solstices falling to the left or right of the shrine through the perfectly-angled placement of the entrance corridor.

At the Palace of Quetzalcoatl in Teotihuacán, the morning equinox light casts a shadow that travels up a feature depicting solar and lunar symbols, such as owls. It's believed that this display is similar in nature to the one at El Castillo at Chichén Itzá.

Cromlech of the Almedres consists of two stone circles of more than 90 granite boulders that date to 6000 BCE, making it among the oldest known megalithic sites in the world and thousands of years older than Stonehenge. 

Situated on an east-facing hill slope nestled in a grove of cork and olive trees, on the morning of the equinox the sun rises along the axis of the monument, casting in-line shadows of the stones.

Basilica San Petronio in Bologna is not just Europe’s sixth-largest church, but also one of the world’s largest solar observatories. This 14th-century Gothic structure houses Cassini’s Meridian Line, a 219ft, brass and copper rail in the floor of the church’s left aisle. It was inlaid by astronomer Giovanni Cassini in 1655. A one-inch hole in the ceiling 88ft above allows a ray of sunlight through, and every day at noon sunlight hits the line somewhere along its length, depending on the time of year. 

At noon of the spring equinox, the light perfectly hits its mark on the floor. Considering that Easter falls on the first Sunday after the first full moon following the spring equinox, it was important to know exactly when the spring equinox took place. This served a religious purpose, but turning the cathedral into a solar observatory also greatly contributed to science.  

At Loughcrew Cairns in County Knowth, the spring equinox sun shines directly into the passage tomb called Cairn T, illuminating a flat boulder covered in petroglyphs. At Carrowmore Megalithic Cemetery in County Sligo, Ireland’s largest megalithic cemetery, the sun rises from behind a saddle in the Ox Mountains, illuminating tombs oriented to the equinoxes.

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