The monumental copper-green dome of Hamburg's brand-new Elbtunnel entrance building — opened in 1911 after four years of extraordinary engineering effort — dominates this hand-colored real-photo postcard, while tucked inside its accompanying box is a miniature leporello accordion-fold souvenir booklet containing black-and-white views of Hamburg's harbor, Rathaus, Navigationschule, Landungsbrücken, Bismarckdenkmal, and the tunnel interior itself, labeled Hamburg, Elbtunnel unter der Erde. The reverse of the main Elbtunnel card (published by Wilhelm Flobe, Hamburg, Nr. 151) carries a detailed German-language description: the tunnel was completed in approximately four years (1907–11) at a cost of roughly 11 million Marks; it is 450 meters long, 20 meters below sea level, and 4.70 meters in diameter, capable of moving up to 14,000 persons per hour via three elevator cars — a marvel of Wilhelmine engineering that still operates today, now a beloved Hamburg landmark and tourist attraction. The leporello booklet, housed in a separate folding card-stock box, expands to reveal a charming accordion sequence of early 20th-century Hamburg scenes, all captioned in German. Together these form a rare, matched souvenir set from the tunnel's opening era.