A farm worker in Rotorua, New Zealand, recently stepped outside to round up cows for milking, and stumbled upon what could be the country’s biggest sinkhole to date.

The massive sinkhole spans the length of two football fields, and is as deep as a six-story building. “The largest I’ve seen prior to this would be about a third of the size of this, so this is really big,” volcanologist Brad Scott told ABC in Australia. “We’ve seen many of these form over the years in this area ... it’s a relatively common occurrence in high intensity rainfall, but this is pretty spectacular.”

According to the National Institute of Water and Atmospheric Research, Rotorua has seen tremendous rainfall recently. Although the rainfall is what spurred the sinkhole’s sudden appearance, Scott said it has been developing for decades.

Sinkholes form when rocks dissolve due to groundwater that circulates underneath, forming caverns underground that can eventually cause the surface to collapse, according to the U.S. Geological Survey.

Beyond its size, this sinkhole is exciting for another reason: It sits in the remains of a 60,000-year-old volcanic crater, Reuters reported, revealing layers of sediments formed by lakes and volcanic ash.