The steepest mile of the top cycling climbs in Spain. From this page you may navigate to the top 5 steepest bicycling climbs in Spain. Spanis steepest bike climbs we have documented are featured in the slideshow below. Scroll down to access Spain's steepest mile Top 10 Bicycle Climbs "Table". The cycling climbs covering the steepest 1 mi gradients in SP, and some of Spain's hardest and most scenic cycling climbs are, in order of steepness, 1. Sierra de Bernia, 2. Alto de l'Angliru, 3. Puerto de Ancares (Pan do Zarco), 4. Casielles, and 5. Xorret de Cati (Castalla).