  We have examined the hypothesis by Bijker and Iachello who asserted that 12C
has an internal structure with three alpha particles arranged in a triangular
shape, leading to the formation of the ground rotational band consisting of 0+,
2+, 3-, 4$^\pm$ and 5- states. Following this idea, we reconstructed the
intrinsic shape of 12C using experimental electron scattering data with minimal
theoretical assumption. Our sole assumption was that the observed 0+, 2+, 3-,
and 4+ states share a common internal structure, forming a rotational spectrum.
The reconstructed intrinsic density showed a beautiful triangular shape with
three peaks implying alpha cluster formation in the ground band.
