All pictures in the header are taken from Bundesarchiv.
1) Plenary hall: Bundesarchiv, photo 102-06066, photographer: not stated
2) Airship: Bundesarchiv, photo 102-06617, photographer: not stated
3) Reichstag building: Bundesarchiv, photo 102-03034, photographer: not stated
4) Persons: Bundesarchiv, photo 116-121-052, photographer: Braatz, Julius
Website of Bundesarchiv