As the sound of prayer echoes across the courtyard thousands gather.
It's impossible to guess how many. Authorities estimate a million people have arrived here over the last 24 hours.
The have made the journey to a shrine in the suburbs of Tehran to remember the life and death of Ayatollah Ruhollah Khomeini.
They have been brought here by bus, by car, and some have come as part of a workplace outing, others under their own steam. Some are here because not coming here would be seen as a social faux pas.
However they got here, they come to show public grief.
For many Ayatollah Khomeini is Iran. The embodiment of the principles of the Islamic Republic. For others he is simply a leader who throughout his life, fought oppression and in exile in France brought about a revolution that deposed the royal family in 1979.
In the West he is seen as the man that toppled a friendly leader that cemented anti-American sentiment in the region, held Americans hostage for over 400 days, and set Iran on a collision course with the west.
As the chants of "Marg Bar Amreka", "Death to the USA" go up you can certainly see why his legacy is divided between what Americans and the West think and what Iranians believe.
Ultimately, both explanations are unsatisfactory.
The anti-American sentiment that is so prevalent at this ceremony is not as bullish as it seems.
There are very few I speak to who genuinely want ill will to befall America.
'We want America to listen'
Ali is a young man in his mid-20's. His wraparound sunglasses and American twang picked up from Hollywood movies is a common look and sound here.
He tells me:
"We chant because for us it's a call that grabs attention, I don't want America to die, we want America to listen to us and not dictate to us."
It's a commonly held opinion I have heard in varying hues from many here.
It perhaps even echoes what Ayatollah Khomeini thought.
He believed that America's domination over the Muslim world had brought about dictatorships and stifled the people.
It would be interesting to know what he would have made of the Arab Spring and fall of some of those dictators.
Today though, is a chance to show national pride and a chance for people to show their love.
When Iran's current supreme leader, Ayatollah Khameini, arrives at the podium the gathered mass stand. For a moment the sound is almost deafening as chants go up...
He pauses... gently waving at the crowd. Even as he begins to speak the fervour of the crowd drowns out his voice. Slowly they settle and the seated leader begins his speech extolling the virtues of Ayatollah Khomeini 's life.
As they listen you can see, by the intense look of concentration on some of the faces, what the man meant to Iran, and why this is such an important date in the calendar.
Here both inside the grand shrine that houses Ayatollah Khomeini and in the courtyard Iranians want to hear their spiritual leader deliver a speech to inspire. He doesn't fail.
He talks of Iran's role in the world and how it has defeated those that would see it suffer. When he mentions Israel as the enemy that would see it suffer, once more the noise of the crowd inside is deafening.
Outside flags flutter, people sit where they can, as volunteers give out food and refreshments.
As the sun shines you could be forgiven for seeing this as celebration but there's still a sense of mourning in the air.
Many are dressed in black... some have tears in their eyes, others clutch pictures of the Ayatollah close to their chests...
This collective grief seems to be heartfelt and genuine.
Perhaps that's why, over 20 years after his death crowds still gather.
Ayatollah Khomeini's vision of Iran as a beacon of Islamic democracy may not be the vision that some believe, it may not be the vision that the west is comfortable with, but it is a vision that still holds true for the people who have made this journey today.
Follow Imran Khan on Twitter: @ajimran