By Michael Bristow
BBC News, Beijing
Hundreds, perhaps thousands, died when China sent in the army
Tiananmen Square is the spiritual heart of China, where people fly kites, pose for photographs and gather on public holidays.
It is also the country's political home; former leader Mao Zedong proclaimed the communist victory from on top of the square's main gate in 1949.
But the word Tiananmen also conjures up more sinister images. It was in and around the square in 1989 that Chinese troops brutally crushed a democracy movement.
There is no reminder on the square today of what happened 20 years ago because the government does its best to ignore the massacre.
But those events are not entirely forgotten. There are some in China who believe there should be a reassessment of what went on.
Dregs of society
One group that risks intimidation from the government by publicly calling for an independent investigation is the Tiananmen Mothers.
This group is made up of parents and relatives of the hundreds of students and ordinary people who were killed when Chinese troops opened fire.
In the run up to the 20th anniversary, it released a public statement to the Chinese leadership calling for those responsible for the killings to be prosecuted.
"The bloody 1989 Tiananmen tragedy was not a result of the government's inappropriate action, but the government's crime against the people," the statement says.
There is little chance the Chinese government will respond to this statement. As far as it is concerned the case is closed.
Immediately after the massacre the government declared that it had been a "counter-revolutionary rebellion" that had to be stopped.
It blamed a small group of troublemakers - the dregs of society it called them - for inciting the majority of noble-minded students.
When referring to the "incident" today, officials choose their words carefully.
At a news briefing last week Chinese Foreign Ministry spokesman Ma Zhaoxu called it a "political incident that took place in the late 1980s".
He rejected the idea that the Chinese government has anything to apologise for.
"It is not appropriate for you to use the word apologise," he told a foreign journalist who had asked a question about the killings.
"Our [communist] party and government have already drawn a clear and unequivocal conclusion," Mr Ma explained.
"Facts have proven that the path taken by China is in line with the actual situation in China and in the interests of the overwhelming majority of people."
But China is reluctant to publicise even its own comments about what went on.
The question and Mr Ma's answer about the massacre did not appear in a written record of the briefing that appeared on the foreign ministry's website.
In China, inconvenient history is sometimes publicly ignored.
A history textbook used by Chinese high school pupils bought by the BBC makes no mention of the events of April, May and June 1989.
Ordinary Chinese people know their government's position and so are wary about discussing the massacre in public.
The BBC recently visited the square to ask people, many of them tourists from outside Beijing, what they knew about the protests.
Many seemed to know little - others knew but did not want to speak to a foreign journalist. Some were pulled away by friends or family members before they could comment.
Not one person was prepared to speak openly and on the record.
But there are Chinese people urging the government to publicly debate the issue.
Cui Weiping, a professor at Beijing Film Academy, recently posted a letter on her blog explaining why China needs to talk about the protests and subsequent massacre.
"We have kept silent about 4 June collectively for such a long time that we are actually participating in concealing this crime," she wrote.
She believes the Chinese Communist Party - despite overseeing 30 years of remarkable economic growth - is still nervous.
"The government is terrified of the people. It doesn't trust the people or have confidence in its own strength," Ms Cui told the BBC in an interview.
But she knows from her own experience as a teacher how difficult it is to discuss the Tiananmen massacre in a public forum.
"I don't initiate conversations about Tiananmen with my students and they don't talk to me about it," she said.
"If I raised this subject with them they wouldn't know what to do. I don't want them to feel embarrassed."
But she said in private it was clear many young people were interested in finding out what went on 20 years ago.
The Tiananmen protests in 1989 were not the first time young Chinese people had staged demonstrations in the square.
At a number of important points in China's turbulent 20th Century, protesters would gather there to make their views known.
The protests 20 years ago were not even the first in Tiananmen in the 1980s, a period in which there was genuine debate throughout Chinese society about political reform.
The events of 3-4 June 1989 changed all that. The period of political openness ended and has not yet returned.
That means there will be no government-organised remembrance ceremonies to mark the 20th anniversary of the Tiananmen massacre this 4 June.
But there will be those who mark the occasion privately - and even the Chinese government will not completely ignore the anniversary.
Publicly it says there is nothing to apologise for, but there is now tight security around Tiananmen Square - an acknowledgement that there are those who disagree with the official position.