[en] Here we report experimental evidence that the high Tc superconductivity in a cuprate perovskite occurs in a superlattice of quantum wires. The structure of the high Tc superconducting CuO₂ plane in Bi₂Sr₂CaCu₂O_8+y (Bi2212) at the mesoscopic level (10-100 A) has been determined. It is decorated by a plurality of parallel superconducting stripes of width L=14± 1 A defined by the domain walls formed by stripes of width W=11+1 A characterized by a 0.17 A shorter Cu-O (apical) distance and a large tilting angle θ =12±4degree of the distorted square pyramids. We show that this particular heterostructure provides the physical mechanism raising Tc from the low temperature range Tc<23K to the high temperature range 30K< Tc<150K. The amplification of the critical temperature of the homogeneous CuO₂ plane by a factor ∼10 is realized by 1) tuning the Fermi level near the bottom of the second ubband of the stripes, with k_y=2π/L, formed by the quantum size effect and 2) by forming a superlattice of wires with domain walls of width W of the order of the superconducting coherence length ξ₀. (author)