In 1898, together with his cousin Paul Cassirer, he opened a gallery and bookshop at 35 Viktoriastraße near Kemperplatz, Berlin.
About 750 m in length, it ran northwards through the Tiergarten park from Kemperplatz (an intersection of roads on the southern edge of the park near Potsdamer Platz), to Königsplatz, in which stood the Berlin Victory Column, in its original position in front of the Reichstag (German Parliament building).