For millenniums, Iran has prospered as a trading hub linking East and West. Now, that role is set to expand in coming years as China unspools its “One Belt, One Road” project, which promises more than $1 trillion in infrastructure investment — bridges, rails, ports and energy — in over 60 countries across Europe, Asia and Africa. Iran, historically a crossroads, is strategically at the center of those plans.

Like pieces of a sprawling geopolitical puzzle, components of China’s infrastructure network are being put in place. In eastern Iran, Chinese workers are busily modernizing one of the country’s major rail routes, standardizing gauge sizes, improving the track bed and rebuilding bridges, with the ultimate goal of connecting Tehran to Turkmenistan and Afghanistan.

Much the same is happening in western Iran, where railroad crews are working to link the capital to Turkey and, eventually, to Europe. Other rail projects will connect Tehran and Mashhad with deepwater ports in the country’s south.