This is a lovely, relaxing two-hour stop while in Key West. You begin the tour after buying your $10 ticket with a butterfly lesson. There is a movie for you to watch about the life cycle of a butterfly. It's very interesting and informative. After the movie, you start the tour of the greenhouse.
It is not a huge greenhouse, but there are so many butterflies that it will take 45 minutes or so to walk through only once (it was incredibly hot the day we went, or we would have walked through another time or two). There are hundreds of butterflies, beautiful plants, and birds in the greenhouse, along with a very relaxing little stream and turtles.
The last part of the greenhouse walks you through the butterfly nursery, where hundreds of cocoons envelope the next generation of greenhouse inhabitants. Since the adult lifespan of a butterfly is only 10 days, the nursery is a busy place.
After the greenhouse, you can visit the gift shop, which is full of everything that is butterflies. All in all, this was a very laid-back, relaxing, and fun activity for a rainy Key West day.