From what I understand, there have been proposals and studies for a bridge linking the Buenos Aires metropolitan area with the area in Uruguay right around Colonia in order to facilitate trade within the Mercosur region, but such a bridge has not been built yet. Is it not built yet because of recurring Argentine instability, or due to the sheer expense and the engineering challenges, or because two studies in the late 1990s came up with two different estimates of tolls and how to finance those (leading to many complications), or for all those reasons? I mean, projects with similar engineering challenges like the Chunnel linking England and France, the Oresund project linking Denmark and Sweden, the Chesapeake Bay Bridge-Tunnel in Virginia (USA), and the Lake Ponchartrain Bridge in Louisiana (USA) have long since been completed.