A riddle in two lines: black within and red without, four corners round about. Let a child guess before giving away that it is a chimney.
From Mother Goose / Nursery Rhymes (traditional). See the whole collection.
Black within and red without;
Four corners round about.
About this rhyme
Rhyme is exactly two lines: 'Black within and red without; Four corners round about' - matches the description exactly (soot black inside, brick red outside).
"A Chimney" is about as short as a riddle rhyme gets: two lines, "black within and red without, four corners round about." It works because a chimney is such an ordinary thing described in a strange way, brick red outside, soot black inside.
Say it slowly and see how quickly a child gets there.
Public domain. Text from The Real Mother Goose (Blanche Fisher Wright, 1916), via Project Gutenberg. View the source edition