Fallout: New Vegas - Old World Blues is the third DLC (direct download content) for Fallout: New Vegas. This time the protagonist visits an old research crater named Big MT in which the greatest minds of the USA were supposed to research in a perfect environment. As expected this doesn't go well for long and so the most new content deals with the subject "mad science".
Besides the story missions the DLC adds new enemies, new perks, new equipment to tinker with and an increased level cap by five. The new area has to be completed before coming back to the main game.