High-temperature superconductivity is often found in the vicinity of antiferromagnetism.This is also true in LaFeAsO1-xFx (x ≤ 0.2) and many other iron-based superconductors,which leads to proposals that superconductivity is mediated by fluctuations associated with the nearby magnetism.Here we report the discovery of a new superconductivity dome without low-energy magnetic fluctuations in LaFeAsO1-xFx with 0.25 ≤ x ≤ 0.75,where the maximal critical temperature Tc at xopt =0.5-0.55 is even higher than that at x ≤ 0.2.By nuclear magnetic resonance and transmission electron microscopy,we show that a C4 rotation symmetry-breaking structural transition takes place for x ＞ 0.5 above To.Our results point to a new paradigm of high temperature superconductivity.