Contents Sort 3 Levels Of Data

I Have a table of Data (WikiData)

WikiIDint
ParentIDint
sTitlevarchar(50)
sDescriptionvarchar(MAX)

There will be three levels of data imposed at the Application Layer

Level 1: ParentID = 0
An Item Like Geography
Level 2: ParentID = a Level 1 WikiID
A sub Topic like Volcanoes
Level 3: ParentID = Level 2 WikiID
A bottom Topic like Pyroclastic Flows

I Need a SQL statement that Will Produce the Output where The output will be produced like this:
Level 1
Level 2
Level 2
Level 2
Level 1
Level 2
Level 2

I Built this but its wrong and has no order by Group by Statements
Select * from WikiData where ParentID = 0 or ParentID IN (Select * from WikiData where ParentID = 0)