The last mountain stage and the final opportunity to change the race. It begins at La Calahorra beneath its Renaissance castle on the edge of the Sierra Nevada and accumulates nearly 4,200 metres of climbing across the day, crossing high ground twice before the finish. The closing ascent to Collado del Alguacil covers 16 km and averages 6.4%, but the average understates it, because the last five kilometres rise more than 500 metres at a gradient above 10%. Whoever holds the red jersey on the evening of stage 20 will almost certainly carry it to Granada, so anyone still needing time has to take it here.