Tilting my fedora at a rakish angle, I affect a gangster pose and swagger into the Mob Museum in Las Vegas. I'm greeted by Oscar Goodman, the former mayor of Vegas, who dreamt up the whole idea. I'd first met Oscar at a reception in London, flanked by two leggy Vegas showgirls. Back then, he had told the assembled guests: "I used to be the mayor. Before that, I was the lawyer to the mob. And now, I sleep with the mayor." (The current mayor is Oscar's wife, Carolyn Goodman.)
A sprightly 73-year-old, Oscar looks very much the suave mob mouthpiece. At the museum's grand opening, on St Valentine's Day last year, he had worn a sharp suit, handmade in Bogota by a tailor who specialised in bullet-proof lining. It was a prudent move, given that shortly after, someone tried to gun him down.
In fact, the attempted hit took place in a fictional episode of TV's CSI, in which Goodman guest-starred as himself, where the plot revolved around the opening of the Mob Museum. I'm hoping life won't imitate art.
The museum, which successfully blends popular culture and history, is the cornerstone of an impressive, if wildly ambitious, $350m (£233m) Downtown Project, led by Tony Hsieh, founder of Zappos online apparel. He describes the project as an urban experiment to build "the most community-focused large city in the world" in Downtown Las Vegas, by investing in property, small businesses and tech start-ups.
Already, the green shoots are sprouting. There's a hipster club here, a bohemian café there, arty boutiques and First Friday, a community-based street arts and performance evening, held, yes, on the first Friday of each month. You can even get mobbed up and plan a hit with like-minded wise guys at the Mob Bar, a block away from the museum.
The museum is housed in one of Vegas's few remaining historic buildings, a handsome old courthouse, where, appropriately enough, hosted the Kefauver Senate committee hearings on organised crime back in the early 1950s. It's laid out as much as possible in chronological order, starting on the top floor.
There are photographs (don't miss The Mob's Greatest Hits wall), video testimonials, films and interactive exhibits such as a deafening machine gun. The second floor opens on to the refurbished courtroom where Oscar defended various mob gods, including Vinnie "The Animal" Ferrara who allegedly committed 26 murders.
Elsewhere, you can be photographed in a line-up, just like a con or a perp. En route, you meet some real charmers, including Leo "The Lips" Moceri, Vincent "The Chin" Gigante and Anthony "The Ant" Spilotro. The museum does its best not to glorify organised crime, but violence was inevitably the modus operandi of the Mob.
I later enjoyed a "Spilotro-style skirt steak" modelled after a meal Goodman ate with The Ant during Spilotro's trial for the murder of Billy McCarthy. We're at Oscar's latest venture, Beef, Booze and Broads at the Plaza, one of the city's most opulent, glamorous steakhouses.
Vegas did good by this Jewish boy from Philly, who arrived in 1964 with just $87 in his pocket. After a stint in the DA's office, Oscar started defending reputed mobsters in 1966, telling me that he worked by the principle: "If there's a fee, there's a remedy."
Oscar, who once suggested every man should get a lap dance "to help the economy", also represented such mob heavyweights as accountant Meyer Lansky, who ran with Charlie "Lucky" Luciano and Vegas pioneer Benjamin "Bugsy" Siegel. His memoir, Being Oscar, is out in June.
The Mob Museum is one of a number of attractions that have opened recently as part of the Vegas's Downtown renaissance. Its metamorphosis from a sleepy little desert cowtown to "the entertainment capital of the world" started in the Freemont Street area in the early 1940s, with hotels such as El Cortez, which Siegel and Lansky bought in 1945 and whose tag line is still "Where locals come to play."
Siegel – immortalised by Warren Beatty in the film Bugsy – then invested in a new site seven miles away and built the Flamingo Hotel & Casino, named after his girlfriend, whose nickname was Flamingo. It opened in December 1946 and the now famous Las Vegas "Strip" was born (although Siegel was whacked soon after it opened). As the Strip prospered, Downtown's glitter faded, becoming little more than a pit stop for budget and tour-bus America.
All that is changing. The heart of the new Downtown is the Freemont Street Experience, a pedestrian mall peppered with casinos, shops, concerts and a stunning light show. You can even rise above "Glitter Gulch"– a zipwire below the 90ft vaulted canopy. And if it's neon you want, then over 150 classic Vegas signs are now housed in the Neon Boneyard on North Las Vegas Boulevard – relics of Sin City's fascinating timeline.
A few blocks away in Symphony Park, the Smith Center for the Performing Arts is a sumptuous Art Deco masterpiece, inspired by another Nevada architectural tour de force, the Hoover Dam. It opened in 2010 and has already become a major southwest cultural venue.
As current mayor, Carolyn Goodman, told me, "There is an infectious energy about Downtown where we have young people opening new clubs, bars and restaurants. It really has taken on a life of its own."
It's the ultimate desert mirage, a glittering pleasure dome that revels in the infamous tagline: "What happens in Vegas, stays in Vegas."
It might stay in Vegas, but Vegas never stays still.
Virgin Holidays (0844 557 3849; virginholidays.co.uk) offers four nights at the Golden Nugget Hotel & Casino from £715pp, with Virgin Atlantic flights from Gatwick. BA (0844 493 0787; ba.com) flies from Gatwick and Heathrow.