Cork is a city in south-west Ireland, in the province of Munster. It is the second largest city in the Republic of Ireland. The centre of the city is an island between two channels of the River Lee. The channels meet downstream at the eastern end of the city centre, where the quays and docks along the river lead outwards towards Lough Mahon and Cork Harbour, one of the largest natural harbours in the world. It became a friendship city of Shenzhen on July 30, 2013.