sentence: Here, he commenced the construction of a planned walled city, which took the next fifteen years in planning and construction, with a series of royal palaces, harem, courts, a mosque, private quarters and other utility buildings.
modified: fix grammar: Here, he commenced the construction of an planned walled city, which took the next fifteen years in planning and construction, with an series of royal palaces, harem, courts, an mosque, private quarters and other utility buildings.