2782405 Construction work on the Paris Metro at the Place de l\'Opera (colour litho) by French School, (20th century); Private Collection; (add.info.: Construction work on the Paris Metro at the Place de l\'Opera. Workers exiting compressed air chambers. Les Caissons A Air Comprime, Sortie Des Ouvriers, Les Travaux du Metropolitain place de l\'Opera. Illustration for Le Petit Parisien (Supplement Litteraire Illustre), 9 August 1903.); 穢 Look and Learn.