The IDA built a three-quarter scale model of the arch from marble using photographs of the original after the 2,000-year-old monument (below), which was built by the Romans, was blown up by ISIS in October last year.
The model will officially be unveiled by London Mayor Boris Johnson this afternoon and will stay on display for three days before travelling to other cities around the world, including New York.
Roger Michel, executive director of the IDA, said: "These monuments represent the shared history of humanity and stand for a rich and complex past that unites all people."
Michel said the replica would be taken to Palmyra, recaptured from ISIS at the end of March, next year to find a permanent home next to the remains of the original arch.
World Heritage Week began on Monday (18 April) with World Heritage Day, celebrated by UN cultural agency UNESCO and the International Commission on Monuments and Sites.
(Original arch picture credit: JOSEPH EID/AFP/Getty Images)