Curving above the treetops of Biržai Regional Park in northern Lithuania, this unusual structure allows a bird's-eye view of a unique landscape. Built in 2015, the Kirkilai Observation Tower's shape is said to resemble a sinking boat, appropriate in an area dotted with water-filled sinkholes. About 30 of these small lakes can be seen from the top of the tower, nearly 100 feet in the air. These lakes can be up to 36 feet deep and are just some of the thousands of sinkholes identified in the park. Water-soluble rocks like gypsum lie under the soil in this area, and over time they gradually erode, forming caves, which then collapse. In some cases, they fill with water, creating this mesmerizing landscape. The interconnected lakes mirror the surrounding greenery, creating a scenic haven for nature enthusiasts.