the whole length of the axis, and the city's entire underground network reoriented to gravitate towards this new hub (at least one tunnel section, around 220 metres in length, was actually constructed and still exists today, buried some 20 metres beneath the Tiergarten, despite having never seen a train). This was in addition to the S-Bahn North-South Link beneath Potsdamer Platz itself, which went forward to completion, opening in stages in 1939. In the event, a substantial amount of demolition did take place in Potsdamer Straße, between the platz itself and the Landwehrkanal, and this became the location of the one Germania building that actually went forward to a state of virtual completion: architect Theodor Dierksmeier's Haus des Fremdenverkehrs (House of Tourism), basically a giant state-run travel agency. More significantly, its curving eastern facade marked the beginnings of the Runden Platz (Round Platz), a huge circular public space at the point where the North-South Axis and Potsdamer Straße intersected. Additionally, the southern edge of the Tiergarten was to be redefined, with a new road planned to slice through the built-up area immediately to the north of Columbushaus (although Columbushaus itself would remain unscathed); this road would line up with Voßstraße, one block to the north of Leipziger Platz. Here Albert Speer erected Hitler's enormous new Reichskanzlei building, and yet even this was little more than a dry run for an even larger structure some distance further away. Meanwhile, the Nazi influence was no less evident at Potsdamer Platz than anywhere else in Berlin. As well as swastika flags and propaganda everywhere, Nazi-affiliated concerns occupied a great many buildings in the area, especially Columbushaus, where they took over most of the upper floors. As if to emphasise their presence, they used the building to advertise their own weekly publication: a huge neon sign on its roof proclaimed DIE BRAUNE POST – N.S. SONNTAGSZEITUNG (The Brown Post – N.S. Sunday Newspaper), the N.S. standing for Nationalsozialist (National Socialist), i.e. Nazi. Probably Potsdamer Platz's most prominent landmark in the mid-1930s, the sign first appears in photographs dated 1935 but was gone again by 1938. On an even darker note, those Nazi concerns included the Gestapo, who set up a secret prison in an upper part of the building, complete with interrogation and torture rooms. Meanwhile, in another part of the building, the Information Office of the Olympic Games Organising Committee was housed. Here