If you want to do the entire "Camino", which is about 900 km long (from France to Santiago) it will take about 30 days (at 30 km a day).
If you just want to receive the official certificate of pilgrimage (the "Compostela") you’ll have to walk at least 100km (200 km on a bike). A network of shelters offers free lodging and stamps the pilgrims passports which provide evidence of completion.
You’re currently seeing a detail of the Cathedral’s main facade.