In a tangled, narrow maze such as Venice, St. Mark's Square will seem like a bright, beautiful, harmonious area with its 12,000 square meters surrounded by beautiful buildings. It is always beautiful, regardless of the season and time of day or night; I suggest coming back here several times, at different hours of the day, to see how the light and shadows continuously transform it. Its appearance is even more different during big popular festivals, such as the crowded Carnival masked event, or the opposite situation, when the so-called "high waters" raise the level of the lagoon and flood the square, forcing you to cross the square on narrow walkways.
Between a million pigeons, tourists, the café tables, and small orchestras, during daytime the square is always crowded. Consider that the esplanade in front of the cathedral was built starting in the ninth century, and has always more or less had its actual size and shape of a trapezoid, but over time its appearance has definitely changed. In the Middle Ages it had a military aspect and was protected by walls and by the Doge's Palace, which at that time was a castle with towers. Then the walls were replaced by buildings with porticoes and loggias called "Procuratie", and the square was first paved in brick, and later in the 1700s with the current beautiful "carpet" of trachyte blocks which designates a large, rectangular central area.
At the opposite end from the cathedral where the square narrows, a church once stood which was demolished to make way for the Procuratie Nuovissime and the staircase of the Correr Museum at the beginning of the 1800s.
To the right of the cathedral you have Piazzetta St. Mark overlooking the lagoon and standing between the Doge's Palace and the Marciana Library. On the opposite side you can take a selfie in Piazzetta dei Leoni, which takes its name from its two eighteenth-century sculptures.
FUN FACT: this is the only "square" in Venice: all the other squares in the city are called "campi", or "campielli" if they're even smaller. You'll quickly learn the other local terms: the streets are called "calli", the covered passages "sottoporteghi", the streets made from canals are "rio terrà" (which means underground), and the streets bordering the water are called "fondamenta", or foundations.
