What's the tallest mountain in Europe
The tallest mountain in Europe is Mount Elbrus in the Caucasus range, on the Russia–Georgia border region in southern Russia. Its highest summit reaches about 5,642 metres (18,510 feet) above sea level, and it has two summits, the western one being the taller.
Whether Elbrus counts as Europe depends on where you draw the line between Europe and Asia. Most conventions place the boundary along the crest of the Greater Caucasus, which puts Elbrus on the European side. If you count only the Alps or the mountains west of the Caucasus, the highest is Mont Blanc, at about 4,805 metres (15,771 feet), on the French–Italian border.
It's a good example of how a "tallest" answer can turn on a geographic convention rather than a measurement.

Photos via Wikimedia Commons: Вид на Эльбрус по пути в Джилы-Су by Ted.ns, CC BY-SA 4.0.