Perched on top of Mt Katsuyama in the centre of town, the castle dominates the city, as it has for centuries. 惭补迟蝉耻测补尘补-箩艒 is one of Japan's finest surviving castles, and one of the very few with anything interesting to peruse inside: the castle has a treasure trove of artefacts with excellent English-language displays. A ropeway (one way/return 楼270/510) is on hand to whisk you up the hill, though there is a pleasant pathway if you prefer to walk.
It's worth walking down via the back slopes of the castle and stopping off at Ninomaru Shiseki Tei-en in the outer citadel of the fort, consisting of old gardens and modern water features.