Blowup of affine space at the origin
= Blowup of affine space at the origin
{title2=$\operatorname{Bl}_0\mathbb A^n$}
The blowup of $\mathbb A^n$ at the origin is the total space of the tautological line bundle $\mathcal O_{\mathbb P^{n-1}}(-1)$. Its exceptional divisor is the zero section $\mathbb P^{n-1}$, and projection to the direction of a line gives the bundle map to $\mathbb P^{n-1}$.