The seismic response of a set of ten non-equally spaced, non-equally sized, homogeneous blocks partially imbedded in a soft soil layer overlying a hard halfspace is studied numerically and shown to be generally larger, in terms of amplitude, duration and spatial variability than that of the ground in the presence of one block or in the absence of blocks. This is qualitatively similar to observed seismic response in the past at sites such as Mexico City and suggests that the built portion of cities may, under certain conditions, play a significant role in the global seismic response of a city.