My 2yo dd has started making giant nests with all her toys. She will pile them all up in the middle of the floor, arranging prams/trikes etc round the outside, and she spends ages doing this. Once completed she demands to be sat in the centre of the heap and sometimes then rearranges things from the middle so that she can reach everything.
I've never heard of this in a toddler - I have a niggling worry that it might be a sign of insecurity. Or is this normal behaviour?