Before powerful artillery was invented, many cities had protective walls. Since they are not suitable for defense any more, most city walls have been removed.
b ɪ f ɔ ɹ WORD_BOUNDARY p aʊ ə ɹ f ə l WORD_BOUNDARY ɑ ɹ t ɪ l ə ɹ ɹ i WORD_BOUNDARY w ʌ z WORD_BOUNDARY ɪ n v ɛ n t ɪ d WORD_BOUNDARY m ɛ n i WORD_BOUNDARY s ɪ t i z WORD_BOUNDARY h æ d WORD_BOUNDARY p ɹ ə t ɛ k t ɪ v WORD_BOUNDARY w ɔ l z WORD_BOUNDARY s ɪ n s WORD_BOUNDARY ð eɪ WORD_BOUNDARY ɑ ɹ WORD_BOUNDARY n ɑ t WORD_BOUNDARY s uː t ə b ə l WORD_BOUNDARY f ɔ ɹ WORD_BOUNDARY d ɪ f ɛ n s WORD_BOUNDARY ɛ n i WORD_BOUNDARY m ɔ ɹ WORD_BOUNDARY m oʊ s t WORD_BOUNDARY s ɪ t i WORD_BOUNDARY w ɔ l z WORD_BOUNDARY h ʌ v b ɪ n WORD_BOUNDARY ɹ ɪ m uː v d WORD_BOUNDARY