Bali's rice terraces are a beautiful sight on the island, and a great place to view them is Jatiluwih in Tabanan. You have to see the vibrant green with your own eyes to believe it, and it stretches as far as you can see making it even more fantastic.
There are pathways for tourists and small stalls to sit and have a cold drink, but groups are few and far between so it's one of the few places in Bali where life seems to just carry on without too much regard for visitors.
It's possible to go to Jatiluwih for half a day, but a full day or even two walking the rice terraces and surrounding hills is definitely recommended. There are a range of guesthouses and hotels in nearby Munduk, Baturiti and Pupuan, which are all beautiful in their own right.