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.