In the case of Christiansfeld, both Modern Urban Planning and Ideal City were proposed as connections.
But what's the difference between these two?
The current definition of Modern Urban Planning ("WHS where "Town Planning" or "Urban Planning" are cited (using those phrases) in the Statement of OUV, Criteria or description.") does not define "Modern" (colonial towns were often planned too). A new definition of Modern Urban Planning could incorporate:
"The modern origins of urban planning lie in a social movement for urban reform that arose in the latter part of the 19th century as a reaction against the disorder of the industrial city" (britannica.com) > So WHS cannot be from earlier than 1850 (which would leave Christiansfeld out).
The current definition of Ideal City is "The utopian concept of an Ideal City originates in Antiquity, and was often used in the Renaissance and later on providing better living conditions for factory workers e.a.". This seems to hint that an earlier phase was meant (Antiquity - Renaissance).
Crespi d'Adda (late 19th century workers town) seems to belong more to Modern Urban Planning. But where to place New Lanark? Was this an early example of Modern Urban Planning?
Maybe we should split the two along timelines (before and after 1850), or we could even merge them as it seems to be a continuous stream in history.