It sits right on the edge of the old harbour, a great block of coloured glass that seems to change its mind every few minutes. When the sky is grey it turns slate coloured, and when the sun comes off the water it throws back blues and ambers and the odd flash of green. Walk inside and the same glass scatters the light across the floor and the walls, so that even on a dull afternoon there is something happening overhead.
The shell was designed by the artist Olafur Eliasson together with the architects Henning Larsen, and it is built from hundreds of coloured panes shaped after the basalt columns you find along the Icelandic coast. The idea was to make a building that does to light what those cliffs do, breaking it into cells and handing it back in pieces. It works. From across the harbour Harpa reads less like a concert hall and more like a piece of the landscape that has learned a few new tricks.
It almost did not happen. Construction began in 2007, and then in 2008 the banks of the country collapsed and the money for the project disappeared more or less overnight. For a while it stood half built by the water, a glass frame with nothing behind it, and there was a real argument about whether to walk away from it. In the end the state and the city decided to finish it rather than leave a ruin on the harbour, and when it opened in 2011 a lot of people read it as a sign that the country was finding its feet again.
These days it is home to the Iceland Symphony Orchestra and the national opera, but you do not need a ticket to enjoy the best of it. The ground floor is open to anyone, the cafe looks out at the boats, and in the evening the glass is lit from within and turns the whole harbour front into something close to a slow fireworks display. Photographers tend to come at dusk, when the building and the sky are doing roughly the same thing.
You will find it on the waterfront a short walk from the centre, close enough to the Sun Voyager that you can see one from the other. Go near sunset, or after dark when the panels light up, and give yourself time to stand still and watch the colours move across it. It rewards patience more than most buildings do.
A photograph of Harpa carries a little of that story with it, a thing that was nearly lost and then kept. Sign one and send it to someone who is rebuilding something of their own, and the picture says more than the words on it.