Milan
Sforza Castle

A centerpiece of Italian history, Sforza Castle has gates and moats from the medieval city, inner and outer walls, circular towers, courtyards for kids to explore. The first fortress was built by Viscontis in the 14th century. During the Renaissance, in the era of Ludovico Sforza, the castello was a magnificent residence for the duke and court of Milan. In 1499, when the French invaded, Ludovico had to skip town; thereafter the castle was used as a military citadel and army barracks. Napoleon successfully besieged the castle in 1796 when he conquered Milan. Today the castle is a "must see."

Filarete Tower - From the Cairoli metro stop, start the at big splashy fountain in front of the castle, and walk up to the tower gateway, the Filarete Tower, 70 meters high. (Originally there was a drawbridge over the moat.) In the center of the tower is a statue of St. Ambrose, patron saint of Milan; on either side are the Visconti and Sforza coat of arms, a snake/dragon swallowing a person and black imperial eagle.
Tip: To go inside the castle, you can walk through the double-walled gate, the Porta Filarete, but to appreciate the scale of this fortified structure, walk all the way around the castle first. Two round towers of dark gray stone anchor the front corners of the castle, deep moats protect the castle from attack, massive walls are over 4 meters thick and 31 meters high. Here and there, look for the coats of arms of the Sforza and Visconti.
Piazza d'Armi - Just inside from the Porta Filarete is the Piazza d'Armi, where knights jousted and soldiers marched up and down.  Da Vinci's huge clay horse statue stood here, until the French soldiers used it for target practice (and it crumbled).
Cats in the castle - The dry moat in the piazza was part of the first Visconti fortifications, before the castle was expanded over a much larger area. Look for cats napping in the dry moat - the cats live in and around the castle grounds, fed by volunteers.
Museum of Ancient Art (Museo d'Arte Antica) - To get a sense of the long history of Milan, walk through the galleries of this museum, from Roman times, through the Middles Ages and Renaissance eras. Don't miss the impressive statute of Bernabo Visconti on horseback (he was poisoned by an ambitious nephew), and other Gothic tomb monuments. Leonardo da Vinci painted the ceiling in Sala delle Asse (Room of Wooden Panels), decorated with a labyrinth of trees twined with golden ropes, the Sforza coat of arms in the center. On display in the Sala Verde is a super arms and armor collection, including pikes, crossbows, halberds, giant blunderbusses, pistols, swords for dueling, and tombstones of knights.
Parco Sempione - Walk out of the castle through the north gate, the Porta del Barco, to Parco Sempione. Lots of grass, shade trees in the park, it's perfect place to have a picnic lunch after touring the castle.
Aquarium (Acquario) - A small aquarium with tanks of fish that live in northern Italy streams (trout), rivers (sturgeon) and lakes (pike), plus fish of the Mediterranean (moray eels, lobsters, scorpion fish) and Red Sea. The aquarium is free.