Kagawa Prefecture (香川県, Kagawa-ken) is mainly known for two things: being the smallest prefecture in Japan and for its udon noodles.
In fact, Kagawa's Sanuki udon is so famous that the prefecture's tourism PR campaign has been named "Udon Prefecture." But while you make sure to try out their satisfying Sanuki udon, there's more to Kagawa than their somewhat self-deprecating tourism campaign name suggests. 23 of the Shikoku Pilgrimage's 88 temples are within Kagawa's borders, while the Marugame Castle is one of the oldest castles still standing.
Other notable tourist destinations include the historical garden of Ritsurin Park, and Kankakei, famous for its maple trees. And if you're in Kagawa, definitely visit the island of Naoshima, renowned for its many art museums and exhibits surrounded by beautiful natural landscapes.