Researchers may have discovered the world's biggest spider web, a massive subterranean structure spanning over 100 square meters in a sulfur cave on the Albania–Greece border. The multilayered web along a wall near the cave entrance is home to a colony of approximately 69,000 Tegenaria domestica (also known as the domestic house spider) and 42,000 Prinerigone vagans spiders. This is believed to be the first documented case of colonial web formation for both species.

Researchers, including members of the Czech Speleological Society, were exploring sulfur caves in 2022 to survey underground wildlife. In one cavern, they found the huge spider megacity and reported it to other scientists, who made several site visits to learn more about the unusual colony.

The team identified the two species by running DNA tests and studying their morphology. Both are usually solitary, so finding them coexisting in a colony was a major surprise, as several researchers detail in a paper published in the journal Subterranean Biology.