Three Heroes and the Navel of the Earth

From fairy tales, we know what happened long ago, but what was even longer ago? Three heroes are about to find out the answer to this question, even though they haven't asked it. Then something unbelievable happens! Gorynych suddenly finds a dinosaur, and Alyosha Popovich, the Prince, and their horse, Julius, literally fall through the ground. Now they urgently need to figure out how to get them back to the future. And most importantly, they need to find out who or what the mysterious Navel of the Universe is.