The Palazzo Ducale di Sassuolo is one of the most important Barque Residence in Northern Italy. Was built over the medieval castle by the Duke Francesco I d’Este and it was intended to be the Dukes Summer Residence. The inside is beautify frescoed by the French painter Jean Boulanger. The residence had an amazing garden (most of which is lost nowadays) with fountains and topiaries. The “Peschiera” is the most important fountain in the Grotto style, meant to replicate an ancient roman ruin. The Palace is open for visits most of the year. Check the official website for hours and prices.
A Great reference book about the area: