Gravitational lensing as a powerful tool in observational cosmology
Here we consider some of the cosmological applications of gravitational lensing and present a short overview of our recent investigations in this field. We show that both strong and weak gravitational lenses represent the powerful tools in observational cosmology with wide range of applications, such as e.g. for: magnifying and detection of distant objects (i.e. as natural telescopes), measurement of cosmological distances, detection of dark matter, studying the total content of the Universe, constraining the cosmological parameters and investigating the physics and geometry in the innermost regions of galaxies and quasars, close to their central supermassive black holes.