The Carpathians stretch across seven countries, but more than half of the whole mountain range is inside Romania. The highest peak in Romania, Moldoveanu, is 2,544 metres tall - about seven times the height of the Eiffel Tower.
The forests here are special because they have been left alone for a very long time. Some of them are 'old-growth' forests, which means no one has ever chopped them down. The trees are huge and old, and the ground is thick with moss, mushrooms and fallen logs. Scientists from all over Europe come to study them.
Around 6,000 brown bears live in these mountains - the largest brown bear population in Europe outside Russia. Wolves and Eurasian lynx live here too, all in the same forest. It is one of the few places on the continent where all three big predators still walk together in the wild.
Romanians love these mountains. Many families have a small wooden cabin or know a village in the foothills where grandparents live. In winter people ski; in summer they hike, pick wild berries, and listen out for the call of the cuckoo.