Okay, I wouldn’t recommend seeing “The Core”, especially if you are looking for any scientific value, but the idea of exploring the interior of the Earth is quite compelling.
David Stevenson proposes sending a probe the size of a Grapefruit into a self-propogating crack in the rock. While currently infeasible, he raises the important question of exploring beneath the surface. Space probes have sent back data from beyond the Solar System, but no one has drilled more than 10 kilometres into the crust of the earth.