In March, we are traveling from Paris, to Colmar, to Munich by train. I didn't realize how far Verdun was from Comlmar and was disappointed to lose that experience. Any recommendations for World War One sites or memorials near Colmar?
A simple google search "World War I Alsace" brings up this result,
https://en.wikipedia.org/wiki/World_War_I_Memorials_and_Cemeteries_in_Alsace
This, with a good map, of course, ought to give you a start. Your experience should also be based on some reading particularly about the battle of Le Linge.
Until the end of WW1 Colmar, and the rest of Alsace, was in Germany. The border, and all the fighting, was in the Vosges mountains west of Colmar which separate Alsace from the rest of France.
There are many sites, but really need a car to visit them.
Post WW1, but related, would be remnants of the Maginot line. Do a search, there are a number of sites in the area, some only open rarely, but among the group, something should work.
We went to the Ligne Memorial Museum in the Voges Mnts. The museum and surrounding area is very interesting. The site is a collection of French and German trenches and infrastructure from a major battle during WW1. There is also a museum on site. If you're interested in WW1 this definitely worth your time. https://www.vallee-munster.eu/en/discover/culture/museums/F269000079_the-linge-memorial-museum-orbey