Castello Sforzesco (Sforzesco Castle), Milan (must see)

Castello Sforzesco, one of the largest fortresses in Europe, was originally built in the 14th century to house the Duchy of Milan. Despite its long history of battles, invasions, sacking and destruction, the castle has endured and been restored many times. One of its towers, the Filarete tower, once used to store ammunition, famously exploded in 1521 after being struck by lightning, causing many casualties and significant damage to the fortress.

During the Napoleonic era, the castle was severely damaged and used as quarters for troops, including stables in the frescoed rooms on the ground floor of the Corte Ducale. However, following Italy's Unification in the late 19th century, the castle was reconstructed by architect Luca Beltrami and returned to the city of Milan in 1905. Today, it is a prominent hub of art and culture, boasting seven museums accessible to the public.

The interior of is adorned with exquisitely detailed works of art, notably the intricate ceiling fresco in the magnificent Sala delle Asse, painted by Leonardo da Vinci, who was commissioned by his patrons, the Sforza family. The fresco depicts a pergola in a garden with 16 mulberry trees held together by a golden rope.

Why You Should Visit:
Each room herein is a treasure, not only for the exhibited items, but also for the ceiling frescoes which are wonders in their own right.
Entrance to the castle is free, so if you're on a budget, just walk through and admire the courtyards and architecture. As for the "all museums" fee, it is quite reasonable.

Tip:
Exploring the entire Castello Sforzesco, complete with its gardens, may take a few days.
Try to go on Tuesday around 2pm to get free entry (entry on the 1st and 3rd Tuesday of every month is free for all public museums).
There's no way to access the battlements or the "inside" (aside from the museums) except by a guided tour, so consider booking one in advance.