The upper area of Potoška Vala includes the upper part of the canyon from the foot of the peak ridge of Učka downstream to the village of Trebišća with its former mill. The area can be experienced along the Through Potoška vala and Učkari MTB routes, which start in Mošćenice and Mošćenička Draga. The Trebišća-Perun History and Mythology Trail also explains the landscape of the upper area of Potoška Vala.

The relief of the area is characterised by a large number of streams that branch off in a fan-like fashion under the slopes of the peak of Učka, after which they form a single watercourse. The passage of the watercourse down steep slopes has resulted in various geomorphological forms within the canyon, such as waterfalls, cascades and channels, as well as scree along the sides of the slopes.

The landscape of the upper area of Potoška Vala is primarily characterised by a dense and well-developed beech forest that covers almost the entire area. The next most important feature (and the main attraction) is the renovated hamlet of Trebišća with its Mythic Park – a series of artistic interventions in the landscape and an interpretation centre. Trebišća is a historic hamlet located right next to the streambed of the canyon. It features a mill that in the past was of crucial importance to people across the entire Mošćenice area, who used to bring their grain here to be ground.

Another attraction in the area is its atmospheric landscape. In addition to the distinctive natural features, this is created by its associative dimensions.