Photoabsorption of free La3+ ions in the 4d excitation region has been measured using the dual-laser plasma technique. A dramatic strong and broad 4d94f(1P) giant dipole resonance was observed. The interpretation of the results is provided using theoretical techniques which go beyond the independent particle approximation. In particular the strong term dependence for 4f(1P) gives evidence of strong polarization effects for the description of the giant dipole resonance.