While Slovakia and Hungary were both part of the Eastern Bloc, one of the philosophies of the communist ruling parties was taming the natural environment. The Gabčíkovo-Nagymaros dams were a project on part of the Danube which makes up the border of these two states, being an attempt to combine this environmental manipulation with improving relations between the countries, and producing clean electricity while preventing floods.
Environmental and economic concerns led Hungary to try to stop the project and it remains only partially completed, with Slovakia taking alternative actions which involved diverting the Danube into Slovak territory and significantly affecting the water supply in the neighbouring part of Hungary. Ironically this has led to a still-unresolved dispute between the countries. Even when the river is used to bring people together, it does not always work simply.
The rise of skepticism about the project marked a turning point in the downfall of the communist regime, especially in Hungary.