A temporary holocaust monument titled Levenslicht (Lifelight)  created by artist Daan Roosegaarde lights up Rotterdam with 104,000 luminescent memorial stones that represent the 104,000 Dutch holocaust victims of the Nazis during WWII.  The monument, which recalls the Jewish custom of placing stones on gravestones to honor the deceased instead of flowers, comprises specially developed rocks with fluorescent pigments that can light up every few seconds by using invisible ultraviolet light. The memorial was inaugurated in Rotterdam on January 16, 2020, and will then travel from January 22 to February 2, 2020, to 170 municipalities in the Netherlands.