This place was so much fun to visit. It is a must for Route 66 fans and contains a Valentine Diner! For more info: http://www.placesthatwere.com/2015/07/twin-arrows-trading-post.html
I visited in March of 2015. This place is amazing. You will definitely need to bring a breathing mask, as the air is full of dust and probably asbestos. Wear sturdy shoes and bring a strong flashlight and headlamp, or several. It is very dark down there. Be aware that there are many places where you could easily fall and severely injure yourself, so be careful. There is standing water in a lot of places too. For more info, check out an article I wrote about my visit: http://www.placesthatwere.com/2016/01/huge-abandoned-titan-i-icbm-nuclear.html