From Liberty Cove House, this place is good for a day trip. It’s Sarushima Island.
Sarushima (“Monkey Island”) is the only natural island in Tokyo Bay and is a wonderful place for a day trip. It is located less than 2 km off the coast of Yokosuka, and can be reached by a 15 minute ferry ride from Mikasa Pier (next to Mikasa Park) that goes back and forth once an hour. (Round trip 1,300yen for adult)
This island is full of historical and cultural significance. You can trace the lifestyle of Jomon period ( 12,000BC to 14,500BC) and Yayoi period ( 300 BC to 400 AC). There is also French Brick-lined tunnels from Meiji Period (1868 to 1912). Walking in this Island is very nice trekking and suitable children. There is nice BBQ deck and table.