during Mexico City's colonial period
... that during Mexico City's colonial period, so many grand mansions were built that the city gained the nickname of the "City of Palaces"?
... that <b id="mwG38"><a href="./History_of_Mexico_City" id="mwG4A" rel="mw:WikiLink" title="History of Mexico City">during Mexico City's colonial period</a></b>, so many grand mansions were built that the city gained the nickname of the "City of Palaces"?