This is the part that gives the book its power. Enoch doesn't just hear about heaven. He goes. He's lifted up, and he travels through places no human is supposed to see.
He describes walls made of crystal, surrounded by tongues of fire. He passes through a great house, and then a second house even greater than the first — burning hot and cold at the same time. And at the center, a throne, blazing like the sun, too bright to look at directly. This is the throne of God, and Enoch is standing in front of it.
Then the angels take him traveling. He sees the storehouses where the winds are kept. He sees where the sun and moon come and go. He sees a deep, empty place — a prison — where certain stars are locked up because they didn't rise on time. Even the stars, in this book, have to keep the rules.
He sees the places where souls wait after death, sorted and kept until the final judgment. He sees mountains of fire and rivers of flame. Enoch is basically being given the grand tour of how reality is put together, top to bottom.