Rustem Pasha is one of neatest buildings in Istanbul. It differs from other Ottoman mosques in a few ways. First, it's tucked away on a side street near the Spice Bazaar. Second, it's not nearly as large as Sultanahmet or Yeni Camii. Third, the mosque is elevated. Once inside the tile and wood work are exquisite and the feeling of serenity is surprising given how busy the neighborhood is.