Allegory of the Active and Triumphant Church and of the Dominican order, or La Via Veritas. It shows the triumph of the Roman Catholic Church over heresy.
The bottom row right shows Dominican friars preaching and persuading the heathen to accept the true faith. St Thomas Aquinas shows the heretics the true word (open book). Above him are various sins and temptations. The row of dancers is obvious but for the modern viewer some of the other allegories are harder to read: the three next to the violinist represent respectively pride, lust, and avarice. Note the people in the trees above — not so much sinning by stealing than literally picking forbidden fruit.
In the Spanish Chapel of the Santa Maria Novella in Florence