Ice wall commemorates Berlin Wall

(CNN) - Theirs was a divided city, where east was east and west was west.

Then one night, the spell was broken and the world changed. It was 20-years ago on Monday that a desperate and dying East Germany announced an end to travel restrictions.

Within hours, bewildered East German guards flung open the gates of the Berlin Wall and families, separated for decades, reunited, as east met  west in Germany's once and future capital. The anniversary is being celebrated today with concerts and memorials.

Berlin's main observances will be at the Brandenburg Gate - the symbol of German reunification which followed the fall of the wall. Oversized dominoes will be toppled to show how communist governments in Europe collapsed one after another in the fall of 1989. And finally, we have some "chilling" video for you -- it has ties to the Cold War. But it's not what you expect. Let's go to Belgrave Square.

In Belgrave Square, in front of the German Embassy, stands an ice wall that is 11-feet high.

"Ice is not permanent," said Manon Awst, an artist. "It represents time, the passing of time. It refers to the moment itself, when the people from the east were tearing down the wall to get to the west. the wall is not only commemorating this moment, we wanted to  connect it to today, and theme of boundaries and divisions is such a relevant theme today."

In the middle of the road, amongst the rush-hour traffic, the art installation, titled "Work in Progress," is anything but invisible.

They started building at 1 o'clock Monday morning. 140 ice blocks and six hours later, Londoners on their way to work will find, like the Berlin Wall, an ice wall has popped up overnight. This symbol of the Cold War will stand here for the next 24 hours and if by that time it has not melted away, they will knock it down.