Area 51
Area 51 is a secret US military base that operates inside the US. This base is most widely known due to the supposed landing of alien space crafts in the 1950s.
Apparently some Soviet MIG aircraft were spotted flying around the area.
A video has been recorded where a former employee talks about the possibility that the Area might contain an intradimensional portal, from which an alien race will come through to invade Earth. This is very likely to be a false story.