The Conservatory Gardens at the Bellagio is really a must see while in Las Vegas, if you are staying on the strip. If in downtown, I don't know if it is worth the pricey cab ride.
It sits in the middle of the Bellagio hotel and is wonderful. There are plants and flowers I have never seen in my life. Somehow it is quiet and peaceful. It is handicapped friendly and free.
The flowers and plants are changed for various seasons and holidays. You will love it.
Have a great time.