Complex sentence: Kingston is a Canadian city located in Eastern Ontario where the St. Lawrence River flows out of Lake Ontario, and is situated at the mouth of the Cataraqui River (south end of the Rideau Canal).
Split into simpler sentences: Kingston is a Canadian city located in Eastern Ontario where the St. Lawrence River flows out of Lake Ontario. The city is sited at the mouth of the Cataraqui River (south end of the Rideau Canal).