Riddles

Nobody has ever walked this way.What way is that?

I have cities ,but no houses.I have mountains, but no trees.I have water,but no fish.What am I?

What is seen in the middle of March and April that can't be seen at the beginning or end of either month?

What disappears as soon as you name it?

I have keys but no locks and space but no rooms.You can enter but you can't go outside.What am I?