A spectacular mountain stream that begins in the snowy peaks of mountainous Thessaly and is characterized by the combination of wild nature and folk culture throughout its course, the Gropa was traditionally best known as the most difficult mountain road pass in Greece until the tunnel of Gropa that passed through the small mountain Spanoulaki. The area is surrounded by large peaks that form the borders of three prefectures: Trikala, Karditsa, and Arta. To the north lies Avgo, to the west Hatzi, and to the south Karavoula.
The Gropa is formed by many streams, waterfalls, and springs that descend from the smaller mountains of Katuna, Tsoukas, Soufli, Achladia, Xirovouni, and Prophet Ilias. The stream starts from the top and after 3.5 km it meets the large stream of Khira, from where it enters the Palaiokarya gorge and later, after another 3.5 km, it flows into the Portaikos River, below the hill of the Little Castle. The total length of the Gropa Stream is only 7 km, which makes it a great place to explore.
The stream is surrounded by a dense riparian forest of sycamores, willows, maples, alders, elms, poplars, etc. A little higher on the limestone rocks, holly trees, arias, and other oak trees grow, while near the settlements there are walnut trees, apple trees, cherry trees, cherry trees, and other fruit trees. At the highest points of the stream and below the craggy cliff of Gropa stretches a semi-mountainous meadow called Detra, and even higher, some beeches and fir trees start. Many remarkable species of flowers also thrive in the area.
As it flows, the Gropa stream passes south through the three settlements of Palaiokarya: Ano, Mesi, and Kato Palaiokarya. It is noted that in the last settlement, there is also one of the last functioning water mills in the area, while next to it there is also a drying rack for washing clothes, wonderful examples of the style and lifestyle of the mountain culture. On the opposite slope of Alataria, below the shelter of Karavoula runs one of the highest seasonal waterfalls in the area. Lower down, at Katafyli, there is also a small dam that holds back the waters of the stream, right behind the famous stone bridge of Palaiokarya.