Question: Which monument in Oberndorf bei Salzburg is dedicated to a Christmas carol that Franz Xaver Gruber is best known for composing? 
Sentence (from "Franz Xaver Gruber"): Franz Xaver Gruber (25 November 1787 – 7 June 1863), was an Austrian primary school teacher, church organist and composer in the village of Arnsdorf, who is best known for composing the music to "Stille Nacht" ("Silent Night").
Relevant evidence: Yes