Even as India is consumed by its upcoming elections, the world’s biggest, the country is nearing another milestone: It’s set to overtake the U.K. to become the world’s fifth-largest economy. By 2030, its GDP could top $10 trillion. Yet, unusually for such a geographically large and economically vibrant country, India has no states to compare to California in the U.S., China’s Guangdong province or Japan’s Kanto prefecture -- all regions with $1 trillion economies. Nor does it have a city on par with New York or Tokyo, both of which boast bigger economies than countries such as Canada and Indonesia, accounting for over a tenth of national GDP apiece.India’s next leader will have a once-in-a-lifetime chance to change that by transforming the country’s commercial capital, Mumbai. A better one might never come along.Mumbai is the engine of the prosperous western state of Maharashtra, India’s largest regional economy with a GDP somewhere between $350-400 billion; the city contributes well over half the total. For Maharashtra to become a $1 trillion economy, Mumbai would need to double or triple the size of its economy, on the back of its preeminent role in service industries, especially finance. That means competing with the likes of Singapore and Shanghai to attract global banks and other world-class financial institutions to the humid, traffic-choked city.This poses obvious challenges. It’ll require regulatory changes, in particular ending the uncertainty and complexity around taxation for financial services firms, which has led to the bulk of the local fund-management industry moving to Singapore. Maharashtra will also have to establish a first-rate system for resolving commercial disputes, involving everything from fast-track courts to international arbitration.Just as importantly, the chaotic city needs to create an efficient core -- a business district attractive enough for leading global businesses to want to locate there. Dense urban clusters create agglomeration benefits, one of the very few ways available to improve productivity permanently.This is, to say the least, hard to imagine. However much residents love Mumbai’s freewheeling, cosmopolitan spirit, the city is an infrastructural mess. Headlong growth has worsened congestion, air pollution and the general quality of life. Urban planning is mostly an afterthought. Haphazard development and an explosion in car ownership has made parts of the cramped city virtually unnavigable during rush hour, when the average commute from the airport to downtown Mumbai can take over 1.5 hours.However, Mumbai has a unique opportunity to turn its fortunes around. The city’s port, which occupies about 900 hectares along the prime eastern waterfront, is slowly vacating the area because shipping and allied activities have moved elsewhere. Redevelopment plans so far have focused on infrastructure, including a cruise ship terminal. 1 The area could be something much bigger: a means to transform Mumbai into a financial powerhouse on par with Shanghai and Hong Kong.Remember that the City of London occupies only 290 hectares. Canary Wharf , London’s new financial district where most major banks are located, is just over 40 hectares. This tiny area hosts financial services firms that provide 160,000 jobs with an average wage in excess of £100,000, while serving as a magnet for other businesses; those 40 hectares generate economic output of over $50 billion annually. Harvard’s Ed Glaeser shows that the area in midtown Manhattan between 41st and 59th Streets houses 600,000 workers, earning $100,000 on average. In Asia, the central business district of Singapore is built on 184 hectares and the Dubai International Financial Centre on 45 hectares.Working with city and state officials, India’s next government should aim to redevelop the port area into an efficient, dense, walkable cluster offering the high quality of life and green spaces lacking in the rest of the city. The experience of reviving the London Docklands shows what’s possible. Much like Mumbai, the port of London also suffered the impact of containerized traffic in the 1960s. Soon, the entire port closed, leaving nearly 2,000 hectares of land derelict. Redeveloping the area and building Canary Wharf into a global financial center took a coordinated effort from the government, the transport authority and the property developer.A dedicated development authority, the London Docklands Development Corporation, provided focus. Priority was placed on creating buildings with large trading floors, a key need for financial services and, in particular, robust public transport links. The latter allowed for density and access to the labor market of greater London, without worsening road congestion. Indeed, there are only 5,000 parking spaces in Canary Wharf and they are rarely full. Strategic communication efforts were designed to withstand changes in political and economic cycles.The challenge in Mumbai will be greater. Federal structures, overlapping jurisdictions and limited state capacity make change harder. The ghosts of past planning mistakes loom large, while mechanisms to fund infrastructure through the promise of future growth are less mature. The new zone must operate with a plan that emphasizes jobs and economic dynamism, flexibility and mixed use, rather than one that is static and heavily zoned. It will also require greater coordination between government agencies to fully integrate the area with the rest of the city, with dense transportation networks being key.Nonetheless, a big idea such as transforming the waterfront into the National Financial Capital Region could fire up imaginations among bureaucrats, bankers and citizens. What’s more, Mumbai’s port is just one of many public sites that are either unutilized or underutilized. India’s railways, ports, defense services and state-owned companies control hundreds of thousands of hectares, a large proportion of which are unproductive relative to their location in the heart of big cities. Success in Mumbai could potentially unlock much larger tracts of land across the country, boosting the economy and dramatically improving the quality of life in Indian cities. Whoever triumphs at the polls next month shouldn’t let this opportunity slip.(Bimal Patel, a senior visiting fellow at the IDFC Institute, has consulted on the masterplan)This column does not necessarily reflect the opinion of economictimes.com, Bloomberg LP and its owners