Each square sits (or, in some cases, "sat") at the center of a ward, which often shares its name with its square. The lots to the east and west of the squares, flanking the major east-west axis, were considered "trust lots" in the original city plan and intended for large public buildings such as churches, schools, or markets. The remainder of the ward was divided into four areas, called "tythings", each of which was further divided into ten residential lots. This arrangement is illustrated in the "1770 Plan of Savannah", reproduced here, and remains readily visible in the modern aerial photograph above. The distinction between trust lot and residential lot has always been fluid. Some grand homes, such as the well-known Mercer House, stand on trust lots, while many of the residential lots have long hosted commercial properties.