There are two main attractions. It's the church of Notre Dame de Dinant built in Gothic style in the XIII-XIV centuries.
And a massive fortress (Citadelle de Dinant), high on a cliff, built in 1815. You can take a cable car up to the fortress from the promenade. We, on the contrary, parked at the top, looked at the fortress and the scenic views from the viewpoints, and then went down.
Getting there: we parked near the citadel 50.261229, 4.916283, but there are parking lots down by the river, too. There is a train station right in the city center, travel time from Brussels is 1.5 hours.