Me and my friends went there last Winter together with other foreigners thru an agency (Adventure Korea). It is not easy to enter the area (DMZ), I guess we passed thru one or two checkpoints (gate). The easiest way, I guess, is to book thru a known agency. On the area, we are not allowed to take picture at the right side where the South Korean army are located. But free to take picture at the left side or in front of the tunnel entrance. Inside, they restrict visitors from taking photos or videos. Some portions are restricted or closed. The tunnel has low ceiling which is slightly uncomfortable for tall person. That's why they provide a helmet at the entrance to protect your head. Inside, the floor is slightly wet but not slippery. Also, it is well lit and not scary. It is also safe for kids. The place is nice and interesting. I would recommend to visit the small museum outside the tunnel. Also, they have small shop where we were able to buy an authentic North Korean paper bill for souvenir.

The JSA was closed on all of the days we were in Korea so I looked around for opinions on whether to go on the 3rd Tunnel tour without the JSA or find something else. I read about the Cheorwon DMZ area and thought it seemed interesting. Our visit was on a Monday and there were very few other people visiting for a tour. It was a nice experience and definitely was not a touristy area at all so we were able to just take in the history and stories that our guide told us.