Potomac

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The river that goes north-south through Washington DC. It divides the map almost from north to south, and serves as the border for the three areas of the Fallout 3 map: Maryland is on the rivers northern shore, Virginia is on the river's southern shore and DC comprises the southeastern part of the river's course. It empties into the Tidal Basin along with the Anacostia River. Swimming through the Potomac is not recommended, as it is highly radioactive.