1. A method for reconstructing a trajectory at a site by means of a processing server connected to a set of cameras and having access to the video recordings from these cameras, comprising: the processing server configured for implenting a 3D visualization application based on virtual reality and augmented reality based on: a static model of a 3D representation of the site; and a dynamic 3D representation database; the 3D visualization application being configured in order to: determine, in the 3D visualization at a moment T0, the location of an object considered to have been left unattended at the site by an owner, in response to a first instruction from the user; determine at least one camera which is best-positioned for displaying said object; access a video recording from this camera so as to display the recording at a moment t prior to T0, t is determined in response to a second instruction corresponding to the moment when the object was left unattended by an owner; and activate a method for tracking the owner via the recordings from the different cameras from the moment t to the present moment so as to determine the current location of said owner.