Disused Slate Mine Railways (Wales) - These narrow-gauge railways ran deep through the core of the Earth, tunnelling through miles of solid rock. In their heyday at the end of the nineteenth century, these thin tunnels saw up to half a million tons of slate pass through each year – the lifeblood of the Welsh economy.
The United States have so much to offer when it comes to the wonders of nature. One of those things are the national and state parks in which due to certain changes caves have been formed. These ten caves stated below are open to public and visitors can visit them all throughout the year.