What point did the former meridian 0 °, called the Ferro meridian, run through?
Through the Spanish island of El Hierro. El Hierro, nicknamed Isla del Meridiano (the "Meridian Island"), is the smallest and farthest south and west of the Canary Islands. The line of longitude running through El Hierro (Ferro), the westernmost of the Canary Islands, was known in European history as the prime meridian in common use outside of the future British Empire.