Architects Richard Meier and David M. Childs have unveiled a master plan for four buildings, a park and an ice rink on part of an enormous nine-acre site near the United Nations. “They say the designs, filed with the city last week as part of an environmental assessment statement, will restore a sense of the Manhattan grid to the edge of the East River. The project is part of a four-parcel property between 35th and 41st Streets that Sheldon H. Solow, the developer, bought from Con Edison for $630 million in a deal approved last year.”