Takamatsu is a prefectural capital of Kagawa prefecture, which is one of the four prefectures located on Shikoku island. It is the most populous city in Kagawa and second one in Shikoku after Matsuyama of Ehime prefecture.
Although Matsuyama is bigger, Takamatsu is the representative city of Shikoku region due to its location. It is closer to Tokyo and Osaka and before Shikoku was connected by bridge, JNR; Japan National Railway was operating passenger ferries between Takamatsu and Uno in Okayama prefecture. This ferry called Uko ferry was the main way to travel between Honshu and Shikoku islands.
Takamatsu is not an administrative city. There are popular tourist attractions and probably the most famous and popular one is Ritsurin garden. Today Shikoku is connected with Honshu with three bridges, including Seto Great bridge which trains are running on. From Honshu to Takamatsu, take JR's rapid train Marine Liner from Okayama. Or domestic flights to Takamatsu airport.