In much the same way as the Buckingham Fountain, Philadelphia's four squares started out as formal gardens. Three retain formal characteristics:
Rittenhouse Square
Washington Square
Logan
Square Circle
There are also several -- extremely pretty -- small formal gardens embedded into the tapestry of Fairmount Park. For example, this small formal park sits squished between the
Waterworks, the river, and the Cliffs:
The Cliffs themselves are perhaps more semi-formal than formal, in that the fact of the cliff ultimately determined its landscape architecture, but they are still characteristically hewn by man: