After California’s Crowley Lake reservoir was completed in 1941, strange column-like formations were spotted on the water body’s eastern shore. The rising gray and stony cylinders have cracks ringing around them at intervals of about 1 foot and have inspired comparisons to Moorish temples.

With those sort of descriptions out there, it’s not surprising that theories on the origins of the columns have been similarly wide-ranging. Some believed they were just portions of rock that, as luck would have it, were eroded away to form the perfect, rising spirals and arches. Others believed the columns had a connection to the area’s volcanic past.

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To get at these questions, geologists at the University of California, Berkeley, set out to investigate. Using a slew of different methods and equipment, including X-ray analysis and electronic microscopes, applied to samples of the columns, the researchers have found there are tiny spaces throughout them.

Read more: Lake Scientist