The first stop of my trip to Sri Lanka is in the North of Kandy, an area called The Cultural Triangle, famous for its ruined palaces, temples and caves. Here I've visited Dambulla's cave temples and Sigiriya's Lion Rock! A great start that foretaste the wonderful nature and sceneries of this simply amazing country.
Dambulla is famous for its five cave temples decorated with amazing murals. They're open from 7.30am to 7pm and it will take you around 45mins / 1 hour to visit them all. The best murals are in cave 3, cave 2 is the biggest and most spectacular and cave 1 hosts a 14-meter long sleeping Buddha. At the bottom of the steps up to the cave temples stands a Golden Temple of Buddha that claims to be the biggest in Asia but actually is not even the biggest in Sri Lanka :)
15km from Dambulla there is Sigiriya, famous for the Lion Rock! I highly recommend you to but the ticket (around 30USD) and climb it till the top! It will take you around 1.5/2 hours to visit the area, climb the Rock and enjoy the breathtaking view! The best times to visit the Rock is either early morning or late afternoon, less tourists and better light! I've done it around 5pm and was perfect. On the summit there once was the Royal Palace, but now only remain the foundations, a square brick platforms overlooking the green hills.