Rule out Strasbourg. I lived in Strasbourg for a year and know the cathedral well. The 15c clock in the cathedral is not a sundial... It's an astronomical *clock*.
It's conceivable, mind you, that it might include a small detail that is a sundial, sort of for comparison purposes. If so, it cannot be a working dial. The clock is indoors, occupying pretty much the entire east wall of the south transept, which is lit only dimly and indirectly by stained-glass windows: very attractive but not conducive to gnomonics. (Liturgical east and south, that's geographical north-east and south-east.) Bill Thayer LacusCurtius http://www.ukans.edu/history/index/europe/ancient_rome/E/Roman
