In Canto XVIII - Canto XX, we deal with the Eighth circle of Hell, also known as Malebolge. Malebolge is the upper half of the Hell of the Fraudulent and Malicious, which represent the sins of the Leopard.  It is a series of ten ditches, and the souls guilty of simple fraud are sorted into these ditches.  Each ditch is called a Bolgia, which means pouch or ditch, and they're connected by a series of stone dikes.  In the center is  a deep large well, which is the last circle of Hell.

Canto XVIII

Canto XIX

Canto XX