When I was travelling in Sri-Lanka, I really loved this little Jeep tour of the National Park which is full of pachyderms which you can get really close to, much to our childlike delight! The animals live in complete freedom in this natural space, so there’s no bitter aftertaste like you get in some places where the animals are mistreated, plus the tour is very enjoyable.
The park is next to the road to Polonnaruwa, and it's fascinating to watch the elephants wandering peacefully along the edge of the road or crossing the tarmac to get from one side to the other. It doesn't happen often, but my guide said he is sometimes 'chased' by an elephant when he's driving. He told me that elephants can reach speeds of 40 km per hour over a short distance. Good to know if you find yourself chased by an elephant...