Go into Heathrow's Terminal 5 and it still has the feel of a futuristic building - light streams in, the check-in desks run off into the distance.
Nine years after it opened, it still feels fresh.
And yet, perhaps the most remarkable aspect of this famous building is something that you never see.
Go through a locked door, down three sets of steps and through a nondescript door in a concrete wall and you find something extraordinary - an entire, unused, vast train station.
It was built along with the rest of the terminal in 2007 but, unlike the rest of the building, it's never been opened to the public.
Instead it was built in the simple expectation that, one day, it would be needed.
And one day it will - the Great Western Main Line is scheduled to link up with Heathrow in 2022 - all that will be required is a new tunnel at either end of this ghost station and it will be ready to go.
But how do you plan for the impact of Brexit on these sorts of giant projects.
As we stand in this dusty, cavernous station, the chief executive of Heathrow, John Holland-Kaye, has a glint in his eye.
He is planning now to build a third runway, and also to remodel many of Heathrow's other buildings, and he accepts there may not be enough skilled construction workers to satisfy all these projects at the same time.
So he told me that the likes of Heathrow, HS2 and Hinkley Point nuclear power station will "phase" their construction: "The last thing we want to have is for all of us needing exactly the same mechanical skills at the same time."
There is, says Holland-Kaye, a need for "collaboration towards a common goal", and he thinks it could be the start of a new era of British engineering.
He said: "Brexit is a catalyst for us to transform our economy, to look towards the UK for skills rather than going to German companies. It is an opportunity to develop a world-class supply chain that we can export around the world."
The UK is very good at coming up with engineering ideas. What hasn't always been so successful is our ability to transfer those into actual projects.
Take Crossrail, the 26-mile new tunnel under London, linking east and west. It was first proposed in the 1940s and there were detailed plans put forward in the 1970s.
But only now it is actually being constructed. So what can we learn from projects like that?
"We need to just get on with it," says Crossrail's Chairman Sir Terry Morgan.
"It's important to consult but we have a tendency to agonise over the details of projects. Sometimes we worry too much and too long. Other countries just make decisions and get on with it. That's what we need to do."
As we talk, 20 metres below the ground in the heart of London, work goes on around us. Crossrail is running to time and to budget, and it's due to welcome its first trains at the end of next year.
Sir Terry thinks it will become the capital's latest tourist attraction, as well as a key cog to keep the city running, but he also thinks it will provide an engineering legacy.
"Engineers came to work for us because they wanted this on their CV, and they wanted to test themselves. And now they'll go and work on HS2, the Thames Tideway, Heathrow and all the other projects we have on the books.
"People said we wouldn't find the skills we needed, but we've trained 650 apprentices on this project. You have to have tenacity and we, as a country, can develop skills through these big infrastructure projects.
"I don't share the concerns about the impact of Brexit - I think we might start exporting our knowledge to other markets. That's a massive opportunity."