Tideway Tunnel: Ricky visits London's new super sewer

It's called the biggest sewer in Britain's history. The Tideway tunnel under the River Thames is being built to stop sewage from spilling out and polluting the famous river.

For years, water companies have been releasing untreated sewage, the waste that goes down our toilets and sinks, into rivers through things like overflowing storm drains.

It usually happens when there's a significant amount of rainfall.

Earlier this year the government announced a plan to cut down on the amount of sewage released into our waters because of the risk it poses to wildlife and the environment.

London's "super sewer" is almost complete and Newsround was given special access to take a look and speak to the team who are working on it.