The structure of the Ruddlesden-Popper layered perovskite Li2CaTa2O2, known for its high photocatalytic water activity since its discovery in 2008, is reinvestigated. This oxide has been characterized by powder X-ray and neutron thermodiffraction, TEM, second harmonic generation (SHG), and Raman experiments on powders and single crystals. It is shown that it undergoes two structural phase transitions (i) around 220 degrees C, mainly characterized by the progressive emergence of SHG signal at low temperatures, and (ii) at 660 degrees C, mainly characterized by changes of the temperature behavior of lattice parameters and by the emergence of Raman signals that linearly increase on decreasing temperature. It is shown by powder neutron diffraction profile refinements at RT, 400, and 800 degrees C that the space groups of the successive phases of Li2CaTa2O2 are the acentric Pna2(1) (RT <= T <= 220 degrees C), Pnma (220 degrees C <= T <= 660 degrees C), and Cmcm (T >= 660 degrees C). A soft mode associated with the transition to the highest symmetry for this structural arrangement (I4/mmm) is also found in the Raman spectra. All these transitions appear continuous: the high temperature ones can be attributed to progressive vanishings of the octahedra tiltings (displacives) while the transition in the vicinity of 220 degrees C from Pna21 to Pnma exhibits order-disorder character.