sentence1: 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).
sentence2: The US ambassador's residence used to be open to the public. 