I haven't even climbed onto the sliding bed, positioned my head and put on headphones, and this is already one of the most surreal moments of my life. I opt for the "hard cycle" – I'm no wuss - slide into the white metal sphere. The door closes and the magic begins. Is it magic, though? James Turrell himself says not. It's merely your mind responding to what the light is doing.

But that's the thing: within seconds of the flashing lights and soft sounds starting up, I'm no longer sure whether what I'm seeing actually there, or in my mind. The air around me flashes and pulses, I can't tell where the lights are coming from, or even the size of the space. It's like looking through a kaleidoscope, but one that speeds and slows with no rhyme or reason, like a remembered dream. At one point, I realise my eyes are closed, and I try to open them. But they're already open, and never closed in the first place. It just feels like I'm looking through closed lids – that sensation of trying to fall asleep while your mind ticks over. I see parts of flowers and corners of buildings, treetops and pressed shapes. Everything is moving too fast to hold onto – colours I've never seen and have no words for.

It's breathtaking, and when I emerge, blinking, and someone guides me down the steps, everything I look at seems to glow and pulse for whole minutes.

Turrell is adamant that everyone who experiences the Perceptual Cell sees exactly the same thing – even the colour-blind. It's just that we have different vocabularies to express it. And it's an experience that's virtually indescribable, and unforgettable. And the experience is already booked out until January. My only advice is, book now before it's too late.

James Turrell: A Retrospective runs until June 8. Tickets through Ticketek. Visit nga.gov.au for more details.