Pablo Sigismondi, a geographer from Córdoba, Argentina, was kind enough to send us photos of two nice arches in his country. One is called El Arco (The Arch) on Lake Posadas in Santa Cruz Province (NABSQNO 19G 288494 4736998).
The other is near the small village of Pilolil in Neuquén Province (NABSQNO 19H 333895 5610957).