At Devín in Bratislava, the Morava River meets the Danube, creating a striking contrast between their waters. The Morava is often noticeably muddier and more brownish, carrying fine sediment from its drainage basin, whilst the Danube can appear clearer and more blue-green.

The two waters do not mix immediately. Differences in flow, temperature, and sediment allow the contrasting colours to remain visible for a while before gradually blending downstream. This creates the distinctive two-coloured water effect that can be seen at the confluence, especially from above.

The Morava also forms part of the Slovakia–Austria border here, making the meeting of the two rivers both a remarkable natural sight and an important geographical landmark.