This presentation deals with head-on collisions of black holes in the full framework of general relativity. Starting with an overview on basic features of black holes we proceed with applying concepts of the ADM formalism to set up spatial metrics containing black holes of equal and unequal mass. Central to our discussion will be the Weyl curvature of these metrics. Along curves that are locally rotationally symmetric exact evolution equations for the Weyl curvature allow us to compute the time it takes for freely falling observers to fall in any one of the black holes. Additionally we are able to estimate a measure of collision time for freely falling black holes in a fully dynamic scenario.