Croagh Patrick in Co. Mayo is where one of Ireland's most enduring traditions takes place. Each year, on the last Sunday in July, thousands of pilgrims walk up to the summit and down again—many of them on their bare feet. The path they have worn is clearly visible all the way to the top, which stands at 764 metres.
St Patrick himself is said to have fasted for 40 days and 40 nights on the summit of Croagh Patrick (also known as the Reek) in AD 441.
(You can buy a print of this photograph at: https://buff.ly/2nGkeBF)