text: Also within the sprawling grounds of the park are the official residence of the president of the Republic , which dates from 1751 ( guided tours from the Visitor Centre Saturday at 9 : 40am and 4 : 20pm ) , and the US ambassador 's residence , an 18th-century house which was formerly the official residence of the Viceroy 's chief secretary ( not open to the public ) .
  
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  The US ambassador 's residence used to be open to the public .