14. (6 points) As shown in the figure, the side length of the shaded small square is 2, and the side length of the largest outer square is 6. Then the area of square $A B C D$ is $\qquad$
【Analysis】As shown in the figure: Add auxiliary lines. Since the side length of the shaded small square is 2, and the side length of the largest outer square is 6, the large square is divided into 9 small squares. The area of each triangle at the corners of the large square is equivalent to the area of a small square with a side length of 2. Therefore, the area of square $A B C D$ is equivalent to the area of 5 shaded small squares. Then, the area formula for a square can be used to solve the problem.
【Solution】Solution: $2 \times 2 \times 5=20$

Answer: The area of square $A B C D$ is 20.
Therefore, the answer is: 20.