This site, about 1km away from Masjid Quba is where the Jewish tribe of Banu Nadhir resided. Despite having a peace treaty, they conspired against the Muslims and even made an attempt on the life of the Prophet (peace and blessings of Allah be on him). They were expelled from Madinah in 4 AH and fled to Khaiber and Syria.
(more to follow)
References: Wikipedia, History of Madinah Munawwarah – Dr. Muhammad Ilyas Abdul Ghani