Caltanissetta's Archaeological Museum gathers finds from the ancient sites scattered around the Salso valley. The material from Sabucina and Gibil Gabib is the main reason to come, especially if you are trying to make sense of central Sicily before the Greek and Roman layers took over.
The museum is outside the historic centre, near the Abbey of Santo Spirito. It pairs well with a visit to Sabucina if you have a car.