The four-corner pavilion of Bihu Mayflower is located in, typing three numbers.

First of all, Blue Lake is the seven wonders, so the first number is 7. Mayflower is a three-track ship in Britain, so the second number is 3. The four corners pavilion is Song Wu, and there is only one Song Wu in the four corners pavilion, so the last number is 1.

This riddle uses the meaning behind them and requires extensive knowledge and judgment. This is a good crossword puzzle.