The Voidomatis River rises from springs beneath the village of Vikos, at the western end of Vikos Gorge in Epirus. Its waters emerge from the limestone mountains of Tymfi, fed by rain and snow that enter the rock through underground channels. The river is approximately 15 kilometres long and flows west towards the plain of Konitsa, where it joins the Aoos River.

The upper springs lie below the steep walls of Vikos Gorge, within the Northern Pindos mountain region. Downstream, the Voidomatis follows a narrow, wooded valley between limestone slopes. It passes beneath the road bridge connecting Aristi and Papingo, two villages of Zagori, and continues towards the historic stone bridge at Klidonia.

The river's spring-fed flow helps maintain its low water temperature and remarkable clarity. Its course is short, but it connects the deep mountain gorge with the wider valley of the Aoos, forming part of the river system that eventually drains into the Adriatic Sea.

Rafting is an established activity on the Voidomatis, particularly along the five-kilometre section between the Aristi road bridge and the stone bridge of Klidonia. The route follows clear water through a forested valley, with gentle rapids and short stretches of faster current. Organised descents are generally suitable for beginners and families, depending on river conditions. Kayaking is also offered on the same stretch, allowing smaller groups to explore the river.

Hiking provides another way to experience the valley. A marked riverside trail connects the Aristi bridge with Klidonia, following the water beneath plane trees, willows and other woodland. The route is approximately five kilometres long and usually takes two and a half to three hours. It passes rock shelters and the old monastery of Agioi Anargyroi before reaching the stone bridge.

A different walk leads from the village of Vikos down towards the river's springs, at the end of Vikos Gorge. This route offers a closer view of the limestone cliffs and the cold water emerging from the mountain.

The Voidomatis is known for its clear, turquoise water, which flows over pale stones and gravel through a narrow mountain valley. Much of the river is fed by underground springs, keeping its temperature low even during summer. The water's transparency makes the riverbed visible along many stretches, particularly around the Aristi and Klidonia bridges.

A continuous corridor of riverside woodland follows the lower river. Large plane trees grow beside the water, together with willows, alders and other plants suited to the moist valley floor. Their branches provide shade along the walking path, while the surrounding limestone slopes rise above the forest. Small springs and streams add water to the main channel.

The river lies within the protected landscape of the Northern Pindos National Park, which includes the Vikos–Aoos area. Its forests, cliffs and mountain habitats support a wide variety of plants and animals. Along the river itself, the combination of flowing water, woodland and rocky banks creates a distinct environment within the wider mountains of Zagori.

The Voidomatis valley preserves evidence of human activity from prehistoric times. Archaeological work at Boila rock shelter, near the river, has revealed stone tools and other remains associated with people who used the sheltered limestone openings during the Palaeolithic period. These findings show how the river valley provided water and resources for early communities living in the mountains.

Farther downstream stands the monastery of Agioi Anargyroi, a small religious site beside the riverside walking route. Its surviving church and setting among trees and cliffs recall the use of secluded valleys for religious life in Epirus. The monastery can also be seen during some organised rafting excursions.

At the western end of the valley, the stone bridge of Klidonia crosses the Voidomatis. Built in 1853 on the site of an earlier crossing, its single arch reflects the stone-building tradition of Zagori. The bridge connected communities and paths before modern roads reached the valley. Today, it marks the end of the main riverside walking and rafting routes.

Above Vikos Gorge, near the village of Kipoi, a seasonal stream runs down towards the gorge and the Voidomatis. Two old stone bridges cross this stream. The Kokkoros bridge, also called the Noutsos bridge, has a single high arch and dates from the 18th century. The Kalogeriko bridge, also called the Plakidas bridge, has three arches and was built in 1814.