Premise: 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.
Hypothesis: There is no disabled access to the park and visitor centre. 
Label: contradiction