Gernikako Arbola (anthem)
"Gernikako Arbola" is the title of a song in bertso form presented both in Madrid (1853) and by the shrine of Saint Anthony at Urkiola (1854) by the Basque bard José María Iparraguirre, celebrating the Tree of Gernika and the Basque liberties. The song is the unofficial anthem of the Basques, but only the first stanza is sung as the Basque anthem.
Source: Wikipedia — Gernikako Arbola (anthem) (CC BY-SA 4.0)