The star turn of the excellent Diocesan Museum (accessed from inside the Catedral de San Pedro) is a collection of Romanesque and Gothic art rescued from Jaca diocese churches – most notably the recreation of the Bagüés village church whose 11th-century murals amount to one of the finest sets of European Romanesque painting.
The rest of the exhibits are by no means ballast. Check out the musical instruments, and the fine Gothic art upstairs.