We report the realization of a microstructure which leads to very strong high-temperature flux pinning in YBa2Cu3O7 crystals. Aligned discontinuous columns of damaged material, about 50 in diameter and more than 15 m long, are produced by 580-MeV Sn-ion irradiation. The enhancement of flux pinning is largest when the applied magnetic field is aligned with these tracks. At high temperatures and fields the pinning is much greater than that produced by random point defects, and causes a considerable enlargement of the irreversibility region in the H-T plane. © 1991 The American Physical Society.