Binondo is an island bounded by estuaries (​esteros)​ . These esteros mix fresh water from Pasig River and salt water from Manila Bay. They also facilitated the transport of goods such as bananas, coconuts and building materials via ​cascos.​

In ​Noli Me Tangere,​ Ibarra bids farewell to Maria Clara at the azotea overlooking the estero He climbs up the stairs to her azotea to bid his farewell. As he leaves through a bangka manned by Elias, Maria Clara remains at the azotea as Ibarra escapes into the night. Many things about the esteros have changed since Rizal’s time. For one, the esteros are no longer widely used for public transport as it has become a refuse dump. The Pasig River Rehabilitation Commission has made efforts to clean up the esteros, but the campaign has yet to gain mainstream traction.