Most mountain ranges are built along plate boundaries where the plates are crashing together. This collision of tectonic plates can result in a crumpling of the crust (as you find in the Himalayas) or a buckling of the crust over a zone of subduction (subduction being where one tectonic plate is pushed over another).
If you have a collision of tectonic plates without one being subducted under the other, as is the case in the Himalayas, you will have a (geologically) violent crumpling of the Earth and, as we all know, that is where you have the highest mountains of the world.