The oldest building in the park is Ashtown Castle , a former papal residence which has been renovated to house the splendid Phoenix Park Visitor Centre ( open 9 : 30am 6 : 30pm ; adults IRa2 , children IRa1 ; concessions ; disabled access ) , which presents a video and an excellent two-floor exhibition on the history and wildlife of the park .
Ashtown Castle is the oldest building in the park .