I've always thought Narnia (the country) seemed really small, and wondered why the Talking Beasts and fantastic creatures we know from Narnia do not seem to inhabit more of the world.
Also, when you look at a map, it is very clear that we are looking at a small portion of a main land even when Archenland, Calormen, the Lone Islands, etc. are taken into account. I have always wondered who and what lies further west than the map reveals.