Witness one of Cao Bang's most unique and increasingly famous natural landmarks: Angel Eye Mountain (Núi Thủng), also known by its local name Phja Piót. Located in the Trà Lĩnh district within the Non Nuoc Cao Bang Geopark, this mountain is distinguished by a massive, perfectly round hole piercing straight through its peak, creating an incredible "angel eye" effect against the sky.

The mountain stands dramatically amidst a rolling landscape of grassy hills and valleys, often dotted with grazing horses and buffalo, creating a picturesque pastoral scene. Reaching the base often involves navigating rural paths, and hiking up closer to the "eye" itself offers fantastic perspectives, though access can depend on local conditions and guidance. The sheer novelty and beauty of the formation make it a magnet for photographers and adventurers.

While becoming more popular thanks to social media, Angel Eye Mountain still retains an off-the-beaten-path feel compared to Cao Bang's main attractions. Visiting requires a bit more effort, often involving a scenic drive and potentially some hiking or walking through beautiful countryside. It's a rewarding destination for those seeking unique natural wonders and exploring the lesser-known corners of the Cao Bang Geopark.