Text: The very heart of the city's centro storico, it was begun in 1296 under Arnolfo di Cambio, although the imposing green, white, and rosemarble neo-Gothic facade was completed only six centuries later.
Entailment: Construction of the centro storico began in 1296, but the facade was finished six centuries later.
Contradiction: Arnolfo di Cambio began developing the city's centro storico in 1357.