Dynamic url with last part as parameter

Hello,

i'm working on Contao 4.5.10 and need the following:

www.example.com/subfolder/unique_url_param

Everythig that arrives under the subfolder "www.example.com/subfolder/" needs to be served by one file.
In this file i have to call an external API with the unique_url_param, so i need it as a get-param in the template.
But i dont want something like this: http://www.example.com/subfolder.htm...ique_url_param

Has anyone an idea how to solve this problem? I tried to search for a solution, but did't find anything.


Tanks

May be custom routes?