The plans include building new cities and retrofitting existing ones for India's rapidly-urbanized population, with private and overseas funding, in addition to government investment.
India's neighbor and rival, China, has already dedicated $8 billion to a similar idea, and countries including South Korea and the United Arab Emirates have recently built modern cities from scratch.
"Cities in the past were built on riverbanks," Modi explained in a speech in June. "They are now built along highways. But in the future, they will be built based on availability of optical fiber networks and next-generation infrastructure."
India's plan includes 100 new "smart cities," in which information technology provides urban solutions. Electronic sensors checking water levels, traffic patterns and security, for example, can send data to city administrators. Automation of services is a priority in "smart cities" as well.
"We can already anticipate the problems that these cities face and attack them at the source," said Rahul Sharma of IBM. "India has a fantastic opportunity where we can work outside of the shackles of existing technology."
Modi's enthusiasm is short on specifics, though, and some doubt if India -- a country whose urban population is expected to grow to 590 million in 2030, but where many live without basic infrastructure -- can achieve what many consider a science-fiction scheme.
"Having a stable roof over every head, public transportation running on every road, a toilet in every house: I would say that is the smartest city ever," said Rutul Joshi, an urban planning professor. "We have to redefine what is smartness."