The aim of the paper was to examine the sustainable character of a thematic tourist trail, using the example of the Land Flowing with Milk and Honey trail in south-western Poland, whose creators emphasize their commitment to the idea of sustainable development. The trail elements that determine its character were indicated. On the basis of the point grading method modified by the authors, tourist and sustainable attractiveness was analysed both for particular elements and the whole trail. For this purpose, several indices were applied: the product regionality index, thematic trail tourism index, and stay attractiveness index. The final effect was the determination of the thematic trail potential, expressed by the quality and uniqueness of products on the trail and by utilizing trail elements in creating a tourist product of trail character. The results clearly point at high sustainable value of the products that were the basis for the trail design. On the other hand, shortcomings are indicated in terms of translating these resources into an attractive tourist offer, which would keep tourists in the region of the trail for a longer time.