Obama transferred to CC from Occidental College which (poor place) is rarely mentioned by the young senator. Obama also tends to forget/ignore his Columbia affiliation, preferring to mention the fact he attended Harvard's law school.
While at Columbia, he lived off campus (he claims to have spent his first night sleeping in an alley and washing with the homeless next to an open fire hydrant), spent most of his time in Butler Library, and made few friends.
He majored in PoliSci, and claims to have concentrated in "International Relations," a designation which does not exist at Columbia. His professors confirm that he was a brilliant, standout student and that he was an active participant in seminars.
It has been alleged that during his time at CC, Obama was accused of assault by a black woman. The case remained in the student disciplinary system, never making it to court. The outcome is unknown.