Many of the levadas on Madeira run through tunnels dynamited out of the mountainside to get them from north to south. On one walk we started contouring round a hillside that could almost have been Wales. After a while we rounded a bend and entered a tunnel running straight north for a kilometre. It contained the levada and also a steel pipe carrying water for hydro-electric power and took us thirteen minutes to traverse by the light of our flickering torches. We burst out into another world. A rain forest of laurels and giant bilberry shrouded in mist. An almost unspoilt valley of indigenous plant life.