Just 20 minutes south of Ubud is the spectacular Tegenungan, or Blangsinga, Waterfall in Kemenuh Village. It's 15 metres high and falls from the Petanu River than runs past the eastern end of Ubud.
The entrance fee is Rp. 20,000 per person and there are a number of ways to enjoy the view.
For a spot of exercise, you can walk down the long flight of stone stairs from the car park (past the souvenir shops). It's steep but only about 6-7 minutes walk (sandals are fine) with plenty of places to stop for a photo. At the bottom, walk past the day club and out onto the rocks. You there is a change room and you can take a dip in the cooling natural pool, but be careful after a storm and don't let kids go too far in. There is a little temple with a holy spring at the bottom, and a few places to get a coconut and snack.
As always, try getting there early before the tourist rush...it opens at 9am. There is an overpriced swing ($20!) at ground level, but there are also some in the two day clubs.
Now there is debate about how much the day/pool clubs ruin natural places like this. They are loud, and elitist, and expensive. Here are some images to show you how obnoxious they are:
before the day clubs
after D'tukad was built above the falls
now with the western place, Omma.
But the fact is that they are popular, the food is often good and they are great places to sit and enjoy the view.
Omma is the more expensive western option; the food menu is extensive and the coffee is decent. Entrance is free if you eat at the restaurant , and you can use the pool before or after your meal, but getting a poolside lounge, or even eating closer to the pool, is a hefty minimum fee (Rp. 2 million).
For those prices you'll want to plan to stay a few hours. Omma has a convenient lift from the carpark to bypass those stairs. On weekends and high you'll need to book. Website.
D'tukad River Club is the pool bar above the falls; it's a bit more relaxed and local, with cheaper food options and no minimum spend. It's a bit more tucked away, and doesn't take up the visual real estate that Omma does in such an obnoxious way. You can wander easily down to the falls from the bar, and there are some fun swings (from around 40k). Website.
Check our list of Pool Bars in Ubud for more options like these.
There is now a glass airbridge across the river above the falls. It must have cost a bomb as it's a little too pricey; Rp 250k for adults and 125k for kids (although it's cheaper if you are Indonesian). While the view is spectacular, the 5 minutes walk across is not really worth the cost (although it includes an iced tea).
Possibly due to the cost, it's not particularly crowded and the little velvet socks you have to wear are hilarious, so try it out for the amusement value if you could be bothered.
After your waterfall excursion you might like to stop at the Kemenuh Butterfly Park, especially if there are kids in tow. It's a few minutes from the waterfall on the way back to Ubud. Entrance is Rp 100k for adults and 75k for kids. Along with over 500 species of butterflies (kupu kupu), there is a great pool with water slides and a charming tropical garden. I would recommend a swim here for kids rather than at the waterfall. A quite good local restaurant is on the premises and you can stay the night at the lovely Kartika Villas next door. Instagram.
If you have time, opposite the butterfly park is a honey producer offering beekeeping information tours and a little cafe. The stingless bee honey park is a charming spot, and apparently the honey produced by these bees produce highly antioxidant rich honey with neuroprotective effects, which you can, of course, buy at the shop.