<prompt> Translate the following text to EnglishMnamo 1470s, Mehmed aliongeza nguvu za lango la kale kwa kujenga minara mitatu yake mwenyewe, iliyounganishwa na kuta za pazia na minara minne ya Byzantium iliyozunguka Lango la Dhahabu.  <response>: In 1470 Mehmet the Conqueror further strengthened the ancient portal by building three towers of his own, linked by curtain walls to the four Byzantine towers flanking the Golden Gate. 