This is one of the most sacred places on the island for one reason. It is believed that within the castle complex of the last king of Sri Lanka, is an actual tooth relic of the Buddha. It is believed that this tooth was brought down to Sri Lanka from India to ensure the continuance of Buddhism and it has certainly flourished over the past century or so.
There are a variety of things to keep in mind if you are hoping to visit the Temple of The Tooth, during your stay in Kandy. One of the key things to keep in mind is your attire, be sure to follow the dressed codes expressly stated at the entrance to the castle complex or you will not be allowed to enter.
Additionally, keep in mind that there will be a lot of crowds trying to make their way towards the tooth relic so be sure to arrive early to skip the crowds.
If you are staying in a hotel in Kandy Sri Lanka such as the Hunas Falls, be sure to ask for a guide who can fill you in on the overall context and history of this landmark.