Castle #4, also known as Pearl Lake, is a private fish and wildlife pond nestled in Hinsdale, Colorado. Built in 1928, this earth dam stands at a height of 14 feet and spans a length of 1030 feet, providing a storage capacity of 167 acre-feet. With a primary purpose of serving as a fish and wildlife habitat, Castle #4 also caters to recreational activities in the area.

Located on North Clear Creek in South Fork, Colorado, Castle #4 boasts a surface area of 30 acres and a drainage area of 24 square miles. Despite its low hazard potential, the dam has a high risk assessment rating of 2. Although last inspected in 1989, the dam remains in a condition that has not been rated, indicating the need for updated evaluations to ensure its safety and functionality for the surrounding environment.

Water resource and climate enthusiasts will appreciate Castle #4 for its historical significance as a vital structure supporting the local ecosystem and recreational pursuits. As a regulated and inspected dam in Colorado, its presence contributes to the conservation efforts and water management strategies in the region. While its risk assessment highlights the need for ongoing monitoring and maintenance, Castle #4 remains a valuable asset for wildlife preservation and outdoor enjoyment in the picturesque surroundings of Hinsdale County.