Can you recommend some free-hand mapping software?

My son wants to draw made-up maps: drawing the boundaries of the country, making up internal borders, inserting cities, names of regions, rivers, lake, offshore islands.

We don’t want to get any kind of software using real data. He just wants to enter things freehand. Designing fantasy maps, that sort of thing.

Any recommendations? He is using a Windows 7 PC.
Thanks to all

SRM