Most of the caves are 1 qubic meter wide. They have arched shape roof, and it used have the stone doors. It used to be the graves.
Nagaoka 100 Caves (長岡百穴, nagaokahyakuana) is located north of Utsunomiya City. It has 52 caves with stone statues of Kannon. Nagaoka 100 Caves are built around 8th century and they were used to be the graves for people lived here. Kannons was built in later time. It is a very unique spot to see and feel the life of ancient time of Japan.
Tourist Info
There is parking.
Access
0. at Utsunomiya Station
1. use Kanto Bus to Toyosatodaiiriguchi.
2. walk (10 min.)
15 min
New Wave Samurai Movie. 
映画好き集まれ！ 
Most of the caves are 1 qubic meter wide. They have arched shape roof, and it used have the stone doors. It used to be the graves.