Neoclassical architecture is like building with Legos, but instead of colorful blocks, we use white and gray stones to make fancy buildings. In Milan, there were a lot of people who wanted to make buildings that looked like they did a long time ago. They wanted their buildings to be very symmetrical, which means making everything match on both sides. They also wanted to use columns, which are like tall sticks that hold up the roof. These columns were usually in a shape that looks like a peanut or a pencil.
Neoclassical buildings in Milan were also very fancy on the inside. People liked to use marble, which is a shiny rock, on the floors and walls. They also used large chandeliers that hung from the ceiling and looked like they were made from glass. One thing that was different from the olden days was that people started using new things, like elevators, which could take people up to higher floors without having to use the stairs.
Overall, neoclassical architecture in Milan means building fancy, symmetrical buildings with columns and marble floors that look like they were made a very long time ago.