some idea of the wealth of philadelphia may be gained from late georgian mansions like cliveden -lrb- 1767 -rrb- , in germantown , and mount pleasant -lrb- 1762 -rrb- , in fairmount park , the nation 's largest urban park . cliveden , seat of the chew family , still contains chairs and a sofa by thomas affleck , one of the greatest colonial furniture makers .