Text: The importance of Siena's 13th- and 14th-century school of art is best illustrated in the imposing Palazzo Buonsignori's National Art Gallery (Pinacoteca Nazionale).
Entailment: The National Art Gallery illustrates the importance of Siena's 13th- and 14th-century school of art.
Contradiction: The National Art Gallery is just a room in someone's house and not at all imposing.