The classical Kapitsa’s problem of stability of an inverted pendulum subjected to vertical vibration of the support and some generalizations are investigated. The asymptotic method of two-scale expansions allows one to determine the level of vibrations that stabilizes the vertical position of the rod. The cases of inextensible and extensible rod are studied, and a benchmark of results is carried out. An attraction basin of the stable vertical position of the rod is found. Both harmonic and random stationary vibrations of the support are considered, too. Stability and attraction basin of the vertical position for a flexible rod are studied in detail. A single-mode approximation is used for the approximate solution to the nonlinear problem of stability of a flexible rod.