Q: Which one is the highest dam in the world?  

Rogun Dam is an embankment dam under construction on the Vakhsh River in southern Tajikistan. It is one of the planned hydroelectric power plants of Vakhsh Cascade. Over three decades only preliminary construction has been carried out on the dam. Due to its controversial state, construction was suspended in August 2012 pending World Bank reports, but has since then resumed. The dam has drawn complaints from neighbor Uzbekistan, which fears it will negatively impact its lucrative cotton crops. The dispute over the project has contributed significantly to bitter relations between the two former Soviet republics.

This project is under construction, opening date is 2018.

Nurek Dam is 300 m. high and it is the second highest Dam in the world.