Just 60 miles (about 95km) southeast of Pittsburgh, on Interstate 76, Fallingwater is a must-see attraction for visitors in the area. The house, designed by Frank Lloyd Wright in 1935 for retail giant Edgar J. Kaufman, is situated among the waterfalls and woods of the beautiful Bear Run Nature Reserve, and remains the world's best example of what has come to be known as 'organic architecture'. A stupefying achievement, Wright managed to design a fully-functioning personal residence that blends fluidly and harmoniously with its natural setting: the sound of rushing water is a constant, susurrus presence in the house; a boulder juts out into the living room and doubles as a hearth; the windows open outward from the corners of the walls, leaving no panes to obstruct the natural view. Ayn Rand was so inspired by this triumphant feat of individualistic artistic expression, that she largely based her novel The Fountainhead on Wright's ingenuous creation. Fallingwater has been included in Smithsonian magazine's list of '28 places to see before you die' - and visitors to Pennsylvania would be sorely remiss to pass up such an opportunity! Make sure to book well in advance.