I'll add to this post later, but it seems from first glance that the protests got absolutely bigger. Here is a story from the BBC and the Korea Times, ohmynews.com has lots of pics and video in Korean.
From what I can tell, it does seem like 800 to 1 million got out nationwide.
As the Korea Times story above reports:
The culmination of a month of protests drew the largest number of protesters ever, coinciding with the June 10 ``People Power'' struggle in 1987, which forced the military dictatorship to adopt a direct presidential election system. It was the first time in more than two decades that such a large number of people gathered in Seoul and other major cities.The photos are from Oh my news and show some of the magnitude and some of the humor of this thing.
People from all walks of life ― from students and workers to former activists who fought for democracy 21 years ago ― joined the rallies, demanding the government renegotiate the beef deal with the United States.
The coalition of civic groups claimed 1 million citizens participated nationwide, including 500,000 in Seoul alone, while police estimated the total number at around 200,000. Tens of thousands of citizens also held separate gatherings in Busan, Gwangju and dozens of other cities around the country.
``As an witness to all major historic events in the past, I took part in this candlelit vigil to join the call for the renegotiation of the beef agreement,'' said Yoo Chung-sik, 69, who accompanied his 63-year-old wife. ``I wanted to share this spirit of freedom though I'm old.''
Hundreds of students marched from Yonsei University to Seoul Plaza, many with the portrait of the late Lee Han-yeol, a former Yonsei student who died after being injured during the 1987 protest. Activists from that time accompanied them.
``I have a lot of worries because of difficulty getting a job. I came here on foot from my school, even though it's an exam period. It reflects the severity of the beef issue,'' said Kim Tom, 23, a student from Yonsei. ``I thought I should come here instead of going to the library.''
Police closed three main roads leading to Cheong Wa Dae by building a two-story barricade of shipping containers. They welded the containers together, filled them with sand and coated their surfaces with grease to prevent demonstrators marching to the presidential office.
Some 40,000 riot police officers were mobilized at major rally sites.