Dikmen Valley is one of Ankara's more successful attempts to turn a ravine into public space. The park runs between dense residential districts south of the centre, with paths, lawns, water features, and long views up the slopes rather than a single monument to tick off.
It is most useful as a breather from museums and traffic. Come for a walk in the cooler part of the day, especially if you are staying nearby or want to see a lived-in side of Ankara that is less formal than Ulus, Kızılay, or the government quarter.