Jas’ Elsner & Ian Rutherford 
Pilgrimage in Graeco-Roman and Early Christian Antiquity [PDF ebook] 
Seeing the Gods

This book presents a range of case-studies of pilgrimage in Graeco-Roman antiquity, drawing on a wide variety of evidence. It rejects the usual reluctance to accept the category of pilgrimage in pagan polytheism and affirms the significance of sacred mobility not only as an important factor in understanding ancient religion and its topographies but also as vitally ancestral to later Christian practice.