The Deepwater Horizon spill is a "a massive ongoing oil spill stemming from a sea floor oil gusher in the Gulf of Mexico that started with a suspicious oil well blowout on April 20, 2010." As of today, the spill covers at least 2,500 square miles of ocean surface. Which is massive. Bigger than the Bay Area, in fact.

See how it compares to Manhattan, Los Angeles, Rome, London, Paris, and other major cities at Google Earth.