Roughly 8.4 million people live within the Randstad, which is almost half the population of the Netherlands. The conurbation produces around half the country's GDP. By any standard it is one of the densest, wealthiest urban regions in Europe. And yet the late Dutch urbanist Niek de Boer famously argued that the Randstad simply does not exist. There is no Randstad city hall, no Randstad mayor, no Randstad sports team, and no one says they are from the Randstad. They say Amsterdammer, Rotterdammer, Hagenees, Utrechter. Each of the four big cities has its own dialect, its own dominant industries, its own self-image. Amsterdam is the cultural and financial centre, Rotterdam the port and immigrant city, The Hague the seat of government and international tribunals, Utrecht the historic religious and university centre. The Randstad is the relationship between them, not a fifth city built on top.

Dutch planners these days prefer the term Deltametropool, and split the conurbation into two large wings. The Noordvleugel, the North Wing, runs from Haarlem and IJmuiden through Amsterdam to Almere and Utrecht and holds around 3.6 million people. Amsterdam dominates it, both culturally and economically, and the city has begun to market itself as the Amsterdam metropolitan area, the Metropoolregio Amsterdam, in a quiet retreat from the older Randstad language. The Zuidvleugel, the South Wing, stretches roughly 60 kilometres from Dordrecht in the southeast up to Leiden, with The Hague and Rotterdam at its heart and Delft at its geographic centre. About 3.5 million people live there. A new light-rail system, RandstadRail, connects Rotterdam and The Hague directly, and a long-delayed extension of the A4 motorway finally closed the gap south of Delft, giving Rotterdam a second route to Amsterdam via The Hague.

For all the talk of growth, the most important feature of the Randstad may be the empty space at its centre. The Groene Hart, the Green Heart, is a protected zone of polder and meadow inside the ring of cities. Successive national planning laws since the 1950s have shielded it from urban sprawl. Alphen aan den Rijn, Gouda, Woerden, and a string of smaller towns sit on its edges. The reason for the policy is partly aesthetic and partly hydrological: this is some of the lowest, wettest land in the country, and turning it into suburbs would be expensive in money and dangerous in flood risk. The result is a metropolitan region where you can be in central Amsterdam in the morning, sheep country by noon, and on a Rotterdam quay by dinner. Almost no other European conurbation works like this.

Three pieces of infrastructure tie the whole region to the world. The Port of Rotterdam is the world's busiest seaport outside Asia and the largest port in Europe. The Port of Amsterdam is Europe's fourth-busiest. Amsterdam Airport Schiphol is Europe's fourth-busiest airport, with the major hub airline KLM running long-haul connections out of one of the flattest, lowest aerodromes in Europe. The motorway network carries some of the highest traffic volumes on the continent: numbered routes A1, A2, A4, A5, A6, A7, A8, A9, A10, A12, A13, A15, A16, A20, A27, and A28 all start or end inside the ring. Up to 20,000 trucks a day occupy the right lane on the busiest stretches. A 14-lane highway is planned near Utrecht. The Dutch Railways, helped by the dense web of stations across the Randstad, rank top three in Europe for punctuality alongside the Swiss and the Belgians.

The Randstad holds some of the most respected universities in Europe: the University of Amsterdam, VU Amsterdam, Leiden University (the country's oldest), Erasmus University Rotterdam, Utrecht University, and the Delft University of Technology. Together they shape the country's research economy and feed a constant flow of students through the trains. Politically, the wider Randstad leans right and conservative, but the student cities, Amsterdam, Utrecht, Haarlem, Leiden, and Delft, tilt the other way. Government sits in The Hague; broadcasting and media cluster around Hilversum in the Gooi region just east of Amsterdam. Holding it all together, almost unbelievably, is the bicycle. Cycle highways, fietssnelwegen, run between the major cities with priority crossings and grade separations from cars. One stretches the full 50 kilometres between Amsterdam and Utrecht. On a clear morning, the Randstad commute looks like the loose, fluid swirl of a thousand small wheels, which is perhaps the truest portrait the region has of itself.