Bridge and Arch: When Polo describes a bridge stone by stone, and the Khan asks about the "arch," Polo replies: "Without stones, there is no arch." This demonstrates the dialectic: "space" (stones) is necessary for the existence of "space" (arch/idea), but "space" is what gives "space" its function and meaning.
Chessboard Analogy: Kublai Khan attempts to reduce his empire to the "rationality" of a chessboard. But Polo invites him to look more closely at the wood of the board, to find the knots, the wormholes, and the history of the wood. Here, the dialectic shifts from the abstract "space" of the game to the "sensory interiority" and history of the material "space."