The interior of the CRN 60m Blue Eyes yacht. Reuters

Two city-states, Monaco and Singapore, along with Geneva spotted top three places in the world's highly-concentrated cities for ultra-high-net-worth individuals, according to a study.

In Monaco, one out of every 56 people is ultra-high net worth, those whose assets are worth at least US$30 million, the highest density out of the 30 global cities ranked in The Wealth-X City Residential Index 2017.

Wealth X, a global wealth information provider, estimates population, wealth and investable assets for the world's major cities for its findings.

Geneva came in second, with an estimated population of 490,000. It has one ultra-high net worth individual out of every 221 residents.

Singapore, on the other hand, has one super-rich resident living among every 707 people.

New York City still has highest concentration of the ultra-wealthy, overall. A total of 14,574 world's super-rich have their primary homes and/or vacation homes in the Big Apple.

Mumbai and New Delhi have the lowest concentrations of ultra-high-net-worth individuals of the cities modeled. Their burgeoning populations dilute the effect of the surging affluence seen in many cities in BRIC countries, the report said.