If heat rises, why is it always so cold in the mountains?

Hot air rises, while the cooler air sinks to ground level. Then the cool air heats up and rises when it reaches the equator; and the hot air reaches the poles and cools, then also sinks. Why is it then that the the higher up in the atmosphere you are the colder it is? If the hot air currents are higher up, shouldn't it be the other way around?