Jorge Colindres, a freshly cologned and shaven lawyer, handed me a hard hat to take the elevator to the 14th floor of what is now the tallest building on the Honduran island of Roatán — nearly twice what the local building code allows. When construction is complete, Duna Residences will house 82 units overlooking a jungle of palm trees, the Caribbean Sea and several other new buildings that the Honduran government considers illegal.

If Próspera were a normal town, Colindres would be considered its mayor; his title here is “technical secretary.” As we looked out over a clearing in the trees in February, he pointed to the small office complex where he works collecting taxes and managing public finances for the city’s 2,000 or so physical residents and e-residents, many of whom have paid a fee for the option of living in Próspera or remotely incorporating a business there. Nearby is a manufacturing plant that is slated to build modular houses along the coast designed by Zaha Hadid Architects. About a mile in the other direction are some of the city’s businesses: a Bitcoin cafe and education center, a genetics clinic, a scuba shop. A delivery service for food and medical supplies will deploy its drones from this rooftop.

There’s not much else to see yet. But the Delaware-based company that founded this experimental town in 2017 has raised $120 million in investments — including from venture-capital funds backed by the Silicon Valley billionaires Peter Thiel, Sam Altman and Marc Andreessen — to transform the territory, about twice the size of Monaco, into the most developed start-up city in the world. Built in a semiautonomous jurisdiction known as a ZEDE (a Spanish acronym for Zone for Employment and Economic Development), Próspera is a private, for-profit city, with its own government that courts foreign investors through low taxes and light regulation. Businesses can choose a regulatory framework from a menu of 36 countries or customize their own.

A California company offers a Montessori education for approximately 60 students. Security is provided by a private firm of armed guards. An arbitration center staffed by three retired Arizona judges handles dispute resolution. (In order to enter the jurisdiction, I was told I needed to sign an “agreement of coexistence” binding myself to 4,202 pages of rules, violations of which would be subject to the jurisdictional authority of the arbitration center.)