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 a planned walled city, which took the next iffteen years in planning and construction, with a series of royal palaecs, harem, courts, a mosque, private quarters and other utility buildings.