Given a connected topological space $E$, under which conditions is it possible to find a subspace $B$ such that $E$ can be regarded as a (rank $n$) vector bundle over $B$?
Is it possible to find the conditions and the $B$'s if one moves to the more rigid differentiable, holomorphic or algebraic setting?
What if we restrict to the case: dim $E$ = 2, dim $B$ = 1? When is a surface the total space of a line bundle?