COMING UP ON "ROCK CENTER WITH BRIAN WILLIAMS" - MONDAY, DECEMBER 5 AT 10P/9C

Throughout West Africa, the poorest of the poor are rushing to primitive gold pits known as artisanal mines. Working conditions are abysmal, and critics say the biggest price has been paid by the region's children who are being exploited as they work at the mines, and poisoned by mercury used to refine the precious metal. Richard Engel goes into the mines and reports from the West African country of Mali.

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Janette Sadik-Khan is single-handedly either revitalizing or ruining the streets of New York City as its Transportation Commissioner. She is on a mission to tame New York's mean streets. Other cities around the country � and the world - are taking notice. She had the audacity to close off half of Times Square to traffic and as a result, business improved almost overnight. With half of the cars and trucks gone, the 365,000 daily visitors could breathe a little easier. In her quest to reduce the City's carbon footprint and manage New York's notorious traffic, Sadik-Khan has converted 260 miles of City streets into bike lanes. But not everyone is a fan. Harry Smith takes a look at both sides of this story.

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Brian Williams takes a look back, with his week-in-review.

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Jimmy Fallon joins Brian Williams in studio.

David Corvo is the senior executive producer, Rome Hartman is the executive producer and Brian Williams is the anchor and managing editor of �Rock Center with Brian Williams� (Mondays at 10p/9C). Follow us at RockCenterNBC.com, facebook.com/rockcenterNBC and @rockcenterNBC.