Sparkasse Siegen began working with Thomas Kellner in 2010 on a series about Siegerland industrial and heritage architecture. From 2010 to 2016, Sparkasse Siegen commissioned Thomas Kellner to produce a scaled-down edition of architecture from the Siegerland region each year. These included the main building on Morleystrasse, the new building on Siegbogen, the town museum in Freudenberg, the old fire station in Netphen, the Wilnsdorf freeway church, the Kreuztal cultural station and the Upper Castle. This also included the plan for a motif of the Nikolaikirche, which Thomas Kellner photographed once and had to photograph again because of a different format.
Other motifs were also prepared, such as the gas ball, Kindelsberg Tower, Apollo Theater, the Wilnsdorf winding tower, Junkernhees Castle or the Old Railway Station in Netphen Deuz.Seven motifs were realized for Sparkasse Siegen.