Shimizu Keiryū Hiroba (Shimizu Mountain Stream Park)

Shimizu Keiryū Hiroba (Shimizu Mountain Stream Park) is a natural park located in Kimitsu City, Chiba Prefecture, on the Boso Peninsula. The park gained widespread recognition around 2015 when social media posts describing it as resembling a world from Studio Ghibli animations triggered viral interest. The park's centerpiece is the famous Kameiwa Cave (Turtle Rock Cave), which features a round hole in the rock through which a brook flows, creating spectacular sunlight reflections.

The cave was constructed in the 1600s as a tunnel to help irrigate nearby rice fields, though it appears as a natural bridge due to its short length that allows sunlight to shine through. The site became particularly famous for its heart-shaped reflection created when sunlight streams into the cave and reflects on the water onto the cave wall. This phenomenon is most visible during early morning hours, particularly during equinoctial weeks when the sun's angle creates optimal lighting conditions.

The park also features Nomizo Falls (Noumizo Waterfall), where the brook flows through small waterfalls and rapids before and after passing through the cave. The combination of the cave's ethereal lighting effects and the surrounding natural stream environment creates a mystical atmosphere that attracts photographers and nature enthusiasts from across Japan and internationally.

Visitors can explore walking paths throughout the park that provide access to various viewpoints of both the cave and waterfall areas. The site offers excellent opportunities for photography, particularly during specific times when natural lighting creates the most dramatic effects within the cave structure.

The park is accessible by train from Tokyo via JR Kazusa Kameyama Station, which serves as the nearest railway connection. From the station, visitors need additional local transportation to reach the park entrance. The park is located at 1954 Sasa, Kimitsu City. As a national park facility, it maintains open access, though visitors should check current conditions and any temporary restrictions before traveling. The site requires no admission fees for basic park access.