self-referencing table - how to process?

I have a self-referencing table 'Properties' and I want to build a
hierarchy of all properties starting at the lowest in the tree. What is
the best approach to this is Rails?

for example:

"properties" table

id>name>belongs_to_id
1|item1|NULL
2|item 2|1
3|item 3|NULL
4|item 4|2

So how would I retrieve the related rows with ids 1,2,4 in such a way
that I can easily build a tree-like list such as:

1
...2
......4

Thanks,
Lee