Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein mediates viral entry to the host cells and initiates the infection. As the only exposed surface protein, it is a primary target for vaccine development. We combined cryo-electron tomography, subtomogram averaging, and molecular dynamics simulations to visualise and structurally characterise spike proteins on the surface of intact virions. We discover three hinges in the stalk of S protein that endow it with surprising flexibility and can be relevant in the process of binding to the surface of the host cell.