London's entire Tube system is about to grind to a halt as 20,000 workers go on strike over pay.
Only the London Overground, the DLR, and TfL Rail will be running, though even some of these services will be disrupted or closed due to overcrowding, according to an Underground worker.
Basically Londoners: put your walking shoes on.
If you're not used to navigating the city above ground, here's a nifty walking map of central London [PDF]. It's provided by Transport of London, which has a bunch of useful information on its website about the strike.
Citymapper has also released "strike safe" features to help get you find Tube-free routes home.
Transport for London