Piazza San Marco (St. Mark's Square) in Venice is one of the most iconic and visited landmarks in the city. It is famous for its grand architecture, historical significance, and lively atmosphere.

Pros:

1. Stunning Architecture**: Piazza San Marco is home to impressive buildings like St. Mark’s Basilica**, Doge’s Palace**, and the Campanile** (the bell tower). The basilica is renowned for its Byzantine mosaics and opulent design, while the palace showcases Venetian Gothic architecture.

2. Historical Significance**: The square has been Venice’s political and religious heart for centuries. It was historically used for major events, processions, and government affairs, making it a place filled with rich history.

3. Lively Atmosphere**: Visitors appreciate the vibrant energy of the square, with its cafes, musicians, and constant flow of tourists. The square is especially magical at night, when it’s lit up and less crowded.

4. Iconic Landmarks**: Besides the basilica and palace, visitors also love the Torre dell'Orologio (Clock Tower) and the Caffè Florian, one of the oldest cafes in Europe, known for its historic charm and classical music performances.

Cons:

1. Crowds and Tourist Prices**: As one of Venice's most popular tourist spots, Piazza San Marco can get extremely crowded, especially during peak seasons. Many visitors find the prices at cafes and restaurants in the square to be quite high compared to other areas in Venice.

2. Flooding (Acqua Alta)**: Due to its low elevation, Piazza San Marco is prone to frequent flooding during the acqua alta (high tide) season, which can limit accessibility and detract from the experience. Elevated walkways are often set up, but it can still be inconvenient.

3. Over-commercialization**: Some visitors feel that the square has become too commercialized, with too many tourist shops and a loss of its traditional Venetian charm.

Overall:

Piazza San Marco is a must-see for its historical, architectural, and cultural significance. Despite the crowds and high prices, it offers a quintessential Venetian experience that leaves most visitors in awe.