If you only spend one day in Milan, follow this itinerary so that you don't miss out on anything: historical monuments and shopping streets are Milan's musts.
Your first stop is the Basilica of San Lorenzo, one of the oldest churches in Milan. Then, walk to the Basilica of Sant'Ambrogio, a notable church consecrated in 379 with an unusual appearance. Peek inside to see its huge atrium, the tombs and the archaeological items that are housed here. Continue to the 15th-century Dominican church listed on UNESCO World Heritage List - Church of St Maria delle Grazie. This church is a must because it displays the famous mural called The Last Supper by Leonardo da Vinci. The wall with the painting remained standing even after the church was heavily damaged during World War II. You can see it in the museum adjacent to the church, just don't forget to book your ticket ahead.
Next, move to the center of Milan and explore the Sforza Castle, a 15th-century Renaissance building surrounded by massive walls. Originally built as a residence of the Duke of Milan, it now houses many intriguing museums. Visit one of the museums or stroll the nearby English style park. After leaving the castle, walk to the Milan Cathedral past the famous La Scala Theater. The cathedral is a real gem and it is worth the visit despite the long queues. Once you are inside, the numerous marble statues will simply take your breath away.
Your last stop is the Royal Palace. Dating back to the Middle Ages, it now houses a museum with many interesting exhibitions of modern art. To end your day, stroll one of the five streets which make up the prestigious Quadrilatero della Moda district - Via della Spiga. Take a walk here even if you are not buying anything, this narrow pedestrian street is lined with beautiful historic houses.