Sometimes, visitors can see the creatures for themselves. The Joanina Library offers regular guided tours.
The best time to catch a glimpse of a bat is at nightfall. You can attend one of the library’s evening concerts, which usually take place at the start of their dinnertime.
You can also try visiting the library on a rainy day late in the afternoon when the chirps and squawks of the bats can often be heard.
The Joanina isn’t the only library that houses bats. About 125 miles south, just northwest of Lisbon, another colony of bats hangs around the Library at the National Palace of Mafra, which is also approximately 300-years-old.
The colony is mostly made up of gray long-eared bats and some serotine bats. It is unclear when exactly the bats took up residence, but experts believe some have been there for centuries.
The library has a collection of books that were printed before 1501 A.D., so these bats help protect their ancient, delicate pages.
It can be difficult to spot a bat here since this library closes before nightfall. But the library does honor the bats by displaying a small glass case with the taxidermied remains of three of the winged creatures.
