Shakado Kiritoshi is a really beautiful, almost secret place in Kamakura. You can get to it driving if you are very, very brave and there is no parking. Katie and I drove to it a few months ago, but today I walked. I recommend walking. The entrance is just 1.9 kilometers from Kamakura Station or 400 meters from Hokokuji.
According to another website, the tunnel was built around 1200. It is very large. There were no people walking through this morning, so I couldn't use them for scale. The pictures below are from the Kinubari Yama trail. Shakado Kiritoshi is not on the trail, but they are not far from each other. I think they were only 500 meters apart.
There are caves all over Kamakura. This one is quite big. It is just under the peak on Kinubari Yama. When you get to the highest point on the trail you have to make a decision between a trail and stairs. If you choose the stairs to get down, you'll come across this big cave.
The other side of Kinubari Yama is a beautiful dense forest.
This was the view from Kinubari Yama. Fuji wasn't visible this morning.