The radio galaxy 3C 120 appears as one of the best sources to study the emission and propagation of relativistic jets in active galactic nuclei. Muti-wavelength multi-epoch observations suggest that this Seyfert 1 galaxy is probably the result of a merger and presents a jet in precession that originates from the accretion of material onto a super massive central black hole. Thanks to its proximity and high activity it is possible to monitor the rapid changing rich inner jet structure with unprecedented spatial and temporal resolutions through very long baseline interferometry observations. The jet is pointing close to the line of sight, and is most probably interacting very dynamically with a cloud of properties intermediate of those of the broad and narrow emission-line regions.