Hidden Virasoro Symmetry of the Sine Gordon Theory

In the framework of the Sine-Gordon (SG) theory we will present the construction of a dynamical Virasoro symmetry which has nothing to do with the space-time Virasoro symmetry of 2D CFT. Although, it is non-local in the SG field theory, nevertheless it gives rise to a local action on specific N-soliton solution variables. These {\it analytic} variables possess a beautiful geometrical meaning and enter the Form Factor expressions. At the end, we will also give some preliminary hints about the quantisation.