Bute Park is the green lung of the city, stretching along the River Taff directly behind Cardiff Castle, and it’s become a go-to recommendation for guests staying anywhere near the centre — especially families and anyone bringing a dog along. There’s a proper arboretum with some genuinely ancient trees, a network of flat, easy paths that suit buggies and wheelchairs as well as joggers, and enough space to properly stretch your legs after a long drive up the M4.
It links up with the Taff Trail, so if you’re feeling ambitious you can follow the river all the way toward Llandaff Cathedral and the weir, or keep it simple with a loop back past the castle walls.
It’s completely free, which makes it an easy recommendation for contractor guests on a budget or families trying to fill an afternoon without spending anything. There’s a good café (Café Castan) about halfway round if you need a coffee stop, and plenty of open grass for kids to run off energy. Best in late afternoon when the light comes through the trees, but genuinely pleasant any time the rain’s holding off.