0 Euro Citadelle de Besançon

Oberthur Fiduciaire produces these souvenir notes under license from the European Central Bank, which granted formal approval for the 0 Euro series beginning in 2015 — a rare instance of the ECB sanctioning a collectible product bearing genuine euro security features, including the official euro symbol and denomination, on a note with no legal tender status whatsoever. The Besançon citadel, a Vauban fortification completed in the late 17th century and now a UNESCO World Heritage Site, is among the more architecturally significant subjects in the series.

Oberthur prints these to the same security standards as circulating currency, which is precisely the point — and the price premium over similar novelty items reflects it.