One way of doing this would be to manually create the page and include
links
to all of the pages.
Another way would be using the Dynamic Page List extension to
automatically
generate the list of pages based on the namespace.
Which one is best for you would depend on how often you see the list of
pages changing.
Given that I don't want to have to manually update the index page every time a new page is created and added to the namespace, I'd prefer to have some way in which the index page could be generated automatically. This way it would always remain in synch and up-to-date.