WW1 centenary: Lights to go out to mark anniversary
4 August 2014 Last updated at 20:25 BST
People across the UK are being asked to switch off their lights between 22:00 BST and 23:00 BST on Monday and to light candles in a mass act of remembrance.
Blackpool Tower, Westminster Abbey, the Eden Project in Cornwall and the headquarters of the Football Association are among the buildings and organisations taking part in the event organised by 14-18 NOW, the official body overseeing the UK's WW1 commemorations.
Sian Lloyd has been exploring how communities in different parts of the country will be taking part.