Blšanský chlum, Natural monument in Blšany u Loun, Czech Republic.

Blšanský Chlum is a protected natural site that rises to 293 meters near Loun and features varied slopes with distinctive geology. The hill's structure shows layers of subvolcanic rock formations and clay deposits visible on the hillsides.

The hill is a volcanic formation: a short asymmetric ridge of subvolcanic breccia penetrated by limburgite, with columnar basalt exposed in an abandoned quarry near the summit. In 2012 the Ústí Region designated it a natural monument (no. 5747), and it is also a European site of community importance (no. 2792).

The hill serves as a home to rare butterflies and plants that visitors can observe while walking through its slopes. Local ecology shapes how the area looks today, with specific plant communities thriving on the hillsides.

A marked yellow hiking trail leads from Loun to the summit and is straightforward to follow. Sturdy footwear is advisable since parts of the path are steep and the ground can be uneven.

The site hosts specialized plant species like Austrian flax that attract the attention of botanists and nature enthusiasts. These plants thrive here under conditions found in few other places in the region.