ERR News - A riddle in the dark: what has eight legs, is bigger than a coin, and haunts one of Tallinn's most popular medieval attractions? Besides the presumable ghosts of the past, one of Tallinn's most popular medieval attractions turned out to be home to a colony of cave-dwelling spiders a few years ago, and they are still there, reported Eesti Päevaleht. The arachnids in the underground bastion passageways in the Old Town's ring of fortifications are not just any spiders – they are Estonia's biggest species, the European cave spider, widespread worldwide but discovered in Estonia for the first time only in the 1990s. Measuring slightly bigger than a two-euro coin, Meta menardi is harmless to humans and favors pitch-dark places. Arachnophobes should not worry - the specific passages where the spiders were found are currently closed to the public.  The head of the bastion passageways museum, Toomas Abiline, said that the colony was found by chance during renovation work, and has been left undisturbed. For now, the spiders have been publicly celebrated with a series of artwork by Jaan Künnap on display in the museum. Mart Meriste, a professor at the Tallinn University of Technology's Tartu college who is considered the country's own arachnologist, told Eesti Päevaleht that the colony is a rare find in Estonia, which has few suitable habitats for Meta menardi.