"Misa Criolla" and "Alfonsina y el Mar" are probably his best-known compositions. "Misa Criolla" was one of the first masses not in Latin shortly after the Second Vatican Council permitted use of the vernacular in Catholic churches. "The Washington Post" wrote that the "Misa Criolla" is "widely regarded as a stunning artistic achievement, [that] combined Spanish text with indigenous instruments and rhythms". It led to album sales numbering in the millions internationally. Ramírez once told "The Jerusalem Post" how "Misa Criolla" was inspired by a visit to Germany after World War II. While there, he had an encounter with two of 5 sisters (siblings, not nuns), who had regularly risked their lives bringing food to Nazi prisoners in their neighbourhood, which led him to consider writing "a spiritual piece". This would eventually become the "Misa Criolla". The "Misa"—a 16-minute Mass for either male or female soloists, chorus, and traditional instruments—is based on folk genres such as chacarera, carnavalito, and estilo pampeano, with Andean influences and instruments. Ramírez wrote the piece from 1963 to 1964, and it was recorded in 1965 by Philips Records, directed by Ramírez himself with Los Fronterizos as featured performers (Philips 820-39 LP, including "Navidad Nuestra", remastered in 1994 and released by Philips as CD 526 155). It was not publicly performed until 1967 in Düsseldorf, Germany, during a European tour that eventually brought Ariel Ramírez before Pope Paul VI. Other notable recordings feature the solo voices of George Dalaras (1989), José Carreras (1990), and Mercedes Sosa (1999). Plácido Domingo recorded the "Kyrie" (the first movement of the "Misa") with Dominic Miller on guitar (2003). On 12 December 2014, the feast of Our Lady of Guadalupe, it was performed in St. Peter's Basilica, Rome at the invitation of Pope Francis, with Patricia Sosa as the soprano soloist and conducted by Facundo Ramírez, son of the work's composer, who had conducted its first performance in St. Peter's Basilica exactly fifty years before. While not sharing the same worldwide success, "Alfonsina y el Mar" enjoys great popularity in Latin America and Spain, being one of the most regarded songs in Argentinian folk music.