The grand opening is only weeks away but the 15.5 acre complex in the heart of the city looks as though it needs a lot more work. The floor has yet to be laid, the frontages of many of the shops are not yet in place and the tram tracks that run through the site are being laid as we walk by.

But the developer, who has changed US retailing by building vibrant open-air retailing centres instead of bland indoor shopping malls, is in a relaxed mood. “We’ll be ready,” he says, pausing to exchange pleasantries with one of his workers. “We have to be.”

The $400m Americana at Brand is the latest open-air project developed by Caruso Affiliated, Mr Caruso’s privately held group. It is also his most ambitious development. The site has plenty of upmarket retailers, such as Tiffany and Barney’s, but unlike his other projects there is also a residential component: 100 condominiums will go on sale when the complex opens on May 2, while another 283 apartments will be available to rent.

The California real estate market is in a slump, battered by the subprime mortgage collapse. But Mr Caruso, who agrees the property market is “going to stay challenged”, expresses confidence that the condominiums will sell. “We have 100 unique units and we have 2,000 people on a waiting list,” he says. Residents will get a concierge service that can make restaurant reservations or book a massage. “I’m convinced that we will buck the trend in the market and, if I’m wrong, then we will convert the condos to [rental] apartments. We have flexibility.”

Mr Caruso is banking on the Americana replicating the success of his other projects, such as his flagship The Grove, a 575,000 sq ft open-air urban shopping and entertainment district in the heart of Los Angeles. The development redefined US retailing when it opened in 2002, partly because it overturned the notion that popular new shopping destinations had to be built out of town. It has also had a profound influence on the design of other US malls: from this year, every new US mall development will be open to the elements.

A snappy dresser – his construction hard hat has his name on it – and a friend of California governor Arnold Schwarzenegger, Mr Car­uso says there is no grand secret to what makes his sites work. “We build what we like and hope everyone else likes it too.” But he has clearly hit on a winning formula. Sales per square foot at The Grove are 40 per cent higher than the industry average, while more than 90 per cent of all visitors buy something. “For the average mall that figure is something like 52 per cent.”

The décor at the Americana is typically lavish and in keeping with the other Caruso projects across southern California. The imposing dome that will sit on top of the main residential building is sealed in gold leaf at a cost of $100,000, while the floor of the grand lobby is made of marble. Exotic foliage and trees have been planted throughout the site, which has a park and a “dancing” fountain programmed to spray water into the air in time with music.

This kind of attention to detail and the subsequent success of his projects has helped Mr Caruso become one of California’s most celebrated entrepreneurs. After a career as a lawyer, he made the switch to real estate when the firm he was working for went “belly up”.

Starting in 1992 with a 51,000 sq ft indoor mall in Los Angeles, his developments have steadily grown in size. Two years ago his company announced a $1bn development slate for the construction of several properties.

His projects differ sharply from the typical US shopping mall. The malls of the 1970s and 1980s were faceless emporiums that offered convenient shopping under one roof. But at a Caruso property, there is much more going on. The Grove and the Americana both have trams, parks, street theatre and open-air concerts. “I have always been more influenced by the organic nature of how a street and town develop,” he says. “We do a lot of work to make it feel more organic. If anything, I’ve been influenced by the fact that I don’t like malls.” He also draws influence from the great European outdoor piazzas. People “engage with the street”.

At 900,000 sq ft, the Americana is much larger than The Grove. In a nod to the more halcyon days of US retailing in the 1950s, uniformed lift operators will greet visitors. “It’s my first contact with the customer so the elevator operator will ask if there’s anything he can do to help. It sets the tone.”

Like The Grove, the Americana is a mixture of architectural styles but there is a definite nod to the US street of yesteryear. “The idea is to put people in a place that transports them to a better time and re­minds them of a village square or [an] old American town. They may have never been to that place but they will wish they had.” It is a simple strategy: the more comfortable visitors feel, the more they are likely to spend.

He has always stuck to a conservative financing strategy, he says: “Debt is under 50 per cent of asset value – at The Grove it’s about 20 per cent of the asset value – so it’s very conservative. With some of the big real estate investment trusts, it’s more like 70 per cent.”

The popularity of his developments has also pushed up their value. A typical return from a retail tenant might be 12 per cent, he says. “Then, depending on the amount and cost of debt, the return on equity becomes 20, 30, 40 per cent.” This may explain why he has never sold one of his projects. “We haven’t sold one and I don’t intend to.”

He has had plenty of opportunities to expand beyond California but says he is happy concentrating on the west coast. “I’ve got four kids between seven and 18 and at this time in my life I don’t want to be on a plane all the time,” he says. “At the right time, sure. But we’re not short of business and if we can build our property locally, then why not?”