How to create common page in wordpress such that in url it should display after the name of parent page?

I am working on WordPress project where I have different locations and according to those location web-pages comes. So there some are pages which have parent assigned and some pages which are common to all locations and don't have parent assigned. For example

Parent Page assigned :- www.mywebsite.com/paris/event.php www.mywebsite.com/london/event.php

common page (no parent page) :- www.mywebsite.com/about.php

How to create about.php page such that it should be common to all location but in URL it should come as www.mywebsite.com/london/about.php

How I can do that in wordpress ?