The right approach to this problem is to first determine the real dimension by using the given scale factor.
width : (2.5 ft) x 250 = 625 ft
length: (2.0 ft) x 250 = 500 ft
The area of a rectangle is calculated by multiplying the length and the width.
A = (625 ft)(500 ft) ]= 312,500 ft²
Thus, the area of the actual castle in square feet is 312,500.