The bankers' internet site suggest that four bedroom apartments are selling for over US 40 million dollars, and estate agents in Monaco confirm this to be about right.

And they describe the 190,000 US dollars a square metre as 'eye-watering' - a description few people would disagree with, and that buyers will need to be billionaires, or not far off being a billionaire.

The second most expensive street in the world is Severn Road in Hong Kong with prices fetching 120,000 US dollars a square metre, and it isn't until third place that New York features, with Fifth Avenue real estate achieving a mere 80,000 US dollars a square metre - placing it firmly within grasp of some multi-millionaires. The upper East side side of Fifth Avenue is the part that gains most interest, and the site notes that some apartments can reach to 60 million - more than Monaco's Princess Grace Avenue, but being such a long road in comparisom it brings the average below that of Monaco's.

It's back to Europe for the fourth most expensive road, London's Kensington Palace Gardens, where property is fetching 77,000 dollars a square metre, and is symbolic of London where some areas continue to see price rises while others drop. London and Monaco normally vye for the most expensive real estate in Europe.

Helping Monaco's Princess Grace Avenue to be the most expensive street in the world is a mix of British, Russian and Arab money, with the British buyers especially attracted by her tax haven status.

Monaco's tourism is upmarket and exclusive too. In a recent report on Monaco's tourism, the Director General of the tourist office announced that no less than 93 per cent of the Principality's hotel capacity is in the luxury category - more than any other country in the world, and confirming Monaco's status as haven for the wealthy.

Also in the report figures showed that Monaco increased her tourist numbers by 36 per cent between 2004 and 2007, and last year alone saw a 10 per cent increase over 2006.

But good as the figures are, Monaco wants to further increase her tourists numbers. Unusually it's not just the numbers overall she wants to improve on, impressive though they are already - but one categoty in particular.

And it's a category of tourist that Monaco is particularly well placed to attract compared to almost every other country in the world - URI's.

URI's could almost have been a class of tourist specially designed for Monaco and all that she offers - and it stands for Ultra Rich Individuals.

One URI could spend more in a week in Monaco than several hundred average tourists, with the casino in Monte Square quite capable of taking a few hundred thousand Euros off the ultra rich in an evening or two. One URI from Italy was recently reported in a British newspaper as cashing up 700,000 Euros for one evening on the tables!

Monaco has the most expensive street in the world, and looks like she intends to keep at the top of the real estate league with London, Hong Kong and New York for some time.