A colossal iceberg the size of Chicago has broken from a floating glacier in Antarctica, and like a retractable roof at a stadium, the drifting structure has opened up a hidden habitat to the elements.

Back in January, a massive chunk of ice the size of Chicago broke off from an ice sheet on Antarctica’s coast. Exploring the waters this oversized block of ice once covered, scientists found — to their surprise — an abundance of life that was living in the waters that were once beneath that ice.

The newfound ecosystem is filled with sea crabs, octopuses and gigantic sponges, suggesting it may have been thriving for centuries.