(1) The main building of the Municipal Party Committee is in the north of the Youth Activity Center and the northeast of the exhibition hall.

(2) The library is to the east of the Grand Theatre and to the south of the Great Hall of the People.

(3) If you enter the square from the east entrance, you can go south from the entrance, then go west at the end, and you will arrive at the Youth Activity Center.

So the answer is: (1) North, Northeast, (2) Grand Theatre, Great Hall of the People, (3) You can go south from the entrance, go to the end and then go west, and you will arrive at the Youth Activity Center.