THE GREAT WALL OF CHINA <i> by David Graham (Thames and Hudson: $35; 223 pp.).</i>

“Walling in an orchard or a garden is ordinary, but not walling in an empire.” So writes Jorge Luis Borges in his introduction to “The Great Wall of China.” The Wall is so long (33,000 miles), so old (begun in 217 BC), so forbidding and so enigmatic that even Daniel Schwartz, who took the pictures, admits it “cannot be photographed. . . . It is an idea.” Inasmuch as an idea can be portrayed, Schwartz has done a splendid job, tracing the Wall (mystically constructed along “dragon-lines”) westward from the Korean border, up peaks, across icebound loessial plateaus and through the Gobi Desert to a spot of rubble where the last of hundreds of thousands of impressed laborers stopped and said, “Ah, the hell with it.” To understand the Wall is to understand China; Schwartz is only the latest interpreter to take a good run--and fall back.