Why the top of mosques are round? And are the minars made for tradition or for Islamic reason?

In my opinion there is no specific islamic reason for this. Its just a tradition or specific construction style for mosques. For minar's, the main theme may be to adjust the sound speaker at the maximum highet in order to spread the azan voice as far as possible so that maximum people obeyed the order of allah to came for prayer (Namaz) when called.