Brazil and Cuba have inaugurated the first phase of a deepwater sea port, a rare large foreign investment project on the Caribbean island.
The $957m (£577m) overhaul of the port of Mariel, in the west of the capital, Havana, is being financed by Brazil.
It is in the heart of a special economic development zone to which Cuba hopes to lure foreign investment.
The BBC's Sarah Rainsford on the island says the upgrade of the port is the biggest project there for many years.
She adds it marks a major new point in terms of foreign investment, which had been highly limited in Cuba.
The new container terminal is equipped for larger ships passing through an expanded Panama Canal.
It was inaugurated by the Brazilian and Cuban presidents.
"Brazil is proud to partner with Cuba in this, which is the first container-terminal port in the Caribbean with the capacity to integrate into the inter-oceanic logistical chain,'' Brazil's Dilma Rousseff said in Mariel.
Her counterpart, Raul Castro, added: "This container terminal, and the powerful infrastructure accompanying it, are a concrete example of the optimism and confidence with which we Cubans see a socialist and prosperous future."
This first phase was financed largely by the Brazilian development bank BNDES and built by the Brazilian construction company Odebrecht.
The terminal will include a rail and highway support network, and replace Havana as Cuba's most important port.
The sleepy town of Mariel, 45 km (28 miles) west of Havana, is best known as the launch point for a mass exodus in 1980, when about 125,000 Cubans left over six months.
A Cuban government decree establishing the special economic zone there includes significant tax and customs breaks for foreign and local companies.
The Caribbean island hopes it will help to increase exports and create jobs.