While in Sri Lanka, travel like locals, that's try and get into trains from one destination to other as much as possible. It's way too much fun.
The country is well connected with the tracks going as far as Nuwara Eliya, a hill station and tea estate region to the down south and 'beachy' Galle to historical Anuradhapura and far north up-to Jaffna.
We took 'Expo Rail' (book it online as it gets really full) from Colombo to Nanu Oya. The journey lasted for about 5 to 6 hours only because the train has to literally climb the hilly region thus taking all its sweet time. But this is the most exotic journey you might take. The train passes through some 40 odd tunnels, bringing you the best of scenic beauty filled with lush green tea estates and jungles with waterfalls, rivers and some cute villages.
From Nanu oya we took Poddi Menikey to reach Kandy, which takes close to 3 hours of back journey.
From Kandy we were booked to travel by Intercity Express that leaves from Kandy at about 6:30 am and reaches Colombo by 9:00 am. This was an unforgettable journey purely because of our choice of carriage and seats. We were seated in an Observation Saloon, a special carriage at the end of the train that offers breathtaking 180 degrees view of Sri Lanka's gorgeous landscape. At times extremely bumpy and at times skirting the edge of a hill, the train cuts through many tunnels, fields and sleepy towns on its way.
We reached Colombo at 9am sharp and took the local train of 1030 am to Galle. Remember this one is a very tricky train. Despite pre booking, you have to try and get into your boogie and grab a seat as and when you get one. This one has no reservation and come with 'first come first serve' situation.
From Galle we took Rajdhani Express. Advance booking can be done at the Colombo rail station itself.
Train journeys are best in Sri Lanka, and definitely worth trying.