Middle Sister Groundhouse, New Hampshire – In operation from 1927-1948, the Middle Sister Groundhouse is a fire lookout tower located on Middle Sister Mountain, along Middle Sister Trail, near Mount Chocorua, in Albany, New Hampshire. A groundhouse fire tower differs from a typical fire tower in that the lookout cabin is built on the ground, not on top of a tower.
Today, the foundation remains intact and some odds and ends linked to the groundhouse can be found at the site. And a Forest Service radio repeater is inside the foundation, which can be seen in the above image. You can see what this fire tower looked like when it was still in operation here.