The city's waterway network served as the primary means of transport until the late 19th century, when modern roads began to be built. Up until then, most people lived near or on the water, leading the city to be known during the 19th century as the "Venice of the East". Many of these canals have since been filled in or paved over, but others still criss-cross the city, serving as major drainage channels and transport routes. Most canals are now badly polluted, although the BMA has committed to the treatment and cleaning up of several canals.