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Cute, curious, and clever—octopuses have a huge fan base. They are sartorially delightful, changing colors as they travel the ocean floor. Like children, they seem to enjoy playing with balls. And they’re smart enough to twist open jars for treats.

Could they be any more awesome? Apparently, yes. Octopuses are also architects and builders.

Several Chinese universities collaborated on a study to observe 12 Korean common octopuses in a tank—picture an aquatic ant farm—as they created their burrows. The researchers also used quick-dry cement to make plaster casts of the Korean common octopus burrows found in nearby mudflats, the cephalopod’s natural environment. The multipart study revealed how and what octopuses build: mazes of complex tunnels with multiple holes for breathing and lounging.

Experts have classified four different types of octopus dens: a well (an open but shallow cavity), a hole (usually an inset under a rock or other heavy object), a mucus-lined den (a deeper tunnel into the earth lined with mucus to ensure structural integrity), and a burrow, the longest and most complicated of these structures. Illustration by Qi-Kang Bo, Jin-Hai Wang, De Xing, Yao-Sen Qian, Min-Peng Song, Xiao-Dong Zheng; Aquatic Biology

Octopuses start the burrowing process by hollowing out the seabed with their arms, widening the holes by sticking most of their arms inside, and using their jet propulsion abilities to kick up loose sand and silt. With each inhalation, octopuses suck water into their bulbous mantles, transporting sand from one end of the tunnel to the other and streamlining the excavation. They drill deeper and deeper, eventually creating a channel that ends with a breathing hole.

Once they have a deep enough channel, octopuses expand a portion of the digging channel to create the lounge, a space big enough to relax their mantles and hide from predators.

Christine Huffard, a marine biologist at Monterey Bay Aquarium Research Institute in California who was not involved in the study, says that “considering the wide range of habitats that octopuses occupy—sand, rock, coral reef, or even kelp holdfasts—this study sparks curiosity about all the different structural engineering skills octopuses must have.”