  Relaxation to equilibrium after strong and collective excitation is studied,
by using a Hamiltonian dynamical system of one dimensional XY model. After an
excitation of a domain of $K$ elements, the excitation is concentrated to fewer
elements, which are made farther away from equilibrium, and the excitation
intensity increases logarithmically with $K$. Equilibrium is reached only after
taking this ``roundabout'' route, with the time for relaxation diverging
asymptotically as $K^\gamma$ with $\gamma \approx 4.2$.
