1 Dollar - Elizabeth II Porta Nigra in Trier

Part of Cook Islands' long-running series of coins with mechanical pop-up inserts, this piece was produced by the Austrian Mint under license — a manufacturing arrangement that accounts for the unusually high production quality relative to the nominal issuer. The Porta Nigra, a 2nd-century Roman gate in Trier, survived medieval demolition largely because a Syrian monk named Simeon walled himself inside it around 1035 AD, after which it was consecrated as a church. Dismantling a church proved politically inconvenient for centuries.