Over the past few days, there have been many protests and events to mark the Nakba. The memory of the flight of those Palestinian refugees has also been captured in a haunting art installation that will be displayed in Jerusalem. It has taken almost a year to put together and is the work of a Scottish artist and thousands of young Palestinians. It makes for one of the most evocative commemorations of this collective tragedy. Al Jazeera's Jacky Rowland reports.