Sea planes are the greatest way to transfer to one location to the other in a real time, rather much quicker if you are in hurry or shorter version of holidays around the country. The scenic flight to down south over the ocean or hills to the central of the island is a life time experience one might love. Sri Lankan Airlines leave Colombo (from Kelani River) and touch down at Mahaweli River in Polgolla, Kandy.
The train journey from Colombo to Kandy is a scenic delight. The epic surroundings of the Highlands will enthrall and some of the views will remain for a lifetime. Intercity express train are hassle free and scenic. Reservation are needed for these trains, it can be done just before the departure depending on the period but is best done in advance especially if you are traveling on a weekend or holiday. There is a great observation saloon (first class) in this particular train. Other trains are overly crowded and late.
If you're just arriving in Sri Lanka, heading for Kandy, you can hire a taxi from one of the stalls in the arrivals hall at Colombo airport. The journey takes about 3 hours from Colombo. This saves the hassle of going into Colombo, and is a lot quicker.