Do you know that every old wrinkled oak is like a whole village, maybe even a city? Beetle larvae gnaw their way under its bark, and baby animals are born there like in a maternity ward - so sometimes it's pretty cheerful and noisy there. Oak even has its own doctor who takes care of it carefully, taps and then listens where it needs healing. In return, they take up residence in it, under the bark in a hollowed out cavity. As neighbors, he has a family of squirrels, an insatiable dormouse, who is properly preparing for the coming of winter in his cell, but also a little owl named Kulišek. From the beautifully illustrated encyclopedia, which is part of the book, you will also learn other interesting facts from the animal kingdom - for example, there is an artist living in a tree who could boldly compete with the best human sculptors... Don't you believe it? So come with us on a visit to the cavities and chambers of the old tree!