From the general theory of relativity it is known that the force of gravitational interaction never exceeds the value Fmax=c2/4G. In this paper we try to make the notion of the force limit intuitively understandable, and illustrate it with thought experiments with such exotic objects as black holes. It was found that maximum limits of force, power, and flow of mass exist in nature. These limits are physically equivalent. All the maximum values could be seen only on a black hole surface. Moreover, maximum limits of force, power, and mass flow are inevitable consequences of properties of the event horizon of a black hole. And vice versa, the existence of black holes could be deduced from the principle of the maximum force. So, these three principles also could be considered as features of a black hole. The role played by the maximum force in general relativity is similar to the role played by speed of light in special relativity.
Keywords: general relativity; maximum force