The New York Times has a nice article (including video) of Nik Wallenda practicing:
Nik Wallenda climbed up a scaffold, stepped onto the steel cable and slipped the harness of his balancing pole over his head. Then he began to walk — each step a few inches in front of the last, his leather moccasins kissing the wire that lay before him.
The backdrop: a T.G.I. Friday’s restaurant, a Starbucks and a Sheraton hotel to the left, and the Seneca Niagara Casino and Hotel to the right.
The scenery next month will be different: the rapids of Niagara Falls swirling below, a cold mist enveloping Mr. Wallenda, a national television audience watching in prime time.
Many in the crowd moved along with Nik Wallenda, slowly, at a distance, as the daredevil walked gingerly atop a high wire over the parking lot at Seneca Niagara Casino.
But the couple of hundred spectators needed to keep their balance on a sidewalk rather than a five-centimetre-wide cable.