That plaza in front of City Hall gets very noisy, even on weekends. The grand avenue that runs next to it leads to the main palace, and is often the place for major protests where riot police confrontations occur. There's usually little actual violence but it's just a noisy place to be and I have been awaken early in the morning on a weekend before from the loudspeakers, and that was from a block away at the Westin Chosun.