Chitwan National Park
Chitwan doesn't look like typical Nepal with rural villages with clay houses, sundown over a river with crocodiles, a wild rhino grazing on the opposite bank. Close to the border with India you can find one of the most beautiful nature parks of whole Asia. You have a good chance of spotting wildlife such as rhino's, bears and even wild elephants and tigers, though chances are rare you will see them. There are many different ways you can explore the park, on foot, by jeep or by elephant. The walking part can be scary at first, when you get survival techniques explained by your guide about what you should do when you are confronted by a very pissed of rhino, but it is a great way to see the park. The jeep ride is fun, it gets you way deeper in the park. The most chances to see and get close to the wildlife is on the back of one of the many elephants.
The elephants are an important source of income for the villagers and get treated pretty well. Go check them out during bathing time, when you can see them enjoying their bath.