Back before the Apollo program was truncated and the last three missions to the moon were cancelled, NASA planners contemplated sending a mission to Crater Tycho, which had some of the most challenging terrain on the lunar surface.
Tycho is a “young” (i.e. 108 million years old) impact crater in the southern highlands on the moon’s nearside. It appears as a bright spot with rays of bright material that stretch across much of the face of the moon. The floor of the crater is rugged and well preserved, thus considered idea for examining how an impact crater forms. Tycho has a central peak that is over one mile high and over nine miles wide.
According to Wired’s Beyond Apollo blog, Tycho was well photographed by a Lunar Orbiter probe that mapped the lunar surface in advance of the Apollo missions. Surveyor 7, an unmanned lander, touched down just a few miles from Tycho’s northern rim on top of one of the ejecta blankets.
An Apollo mission would have landed near the Surveyor landing site. Since the ground was considered too rough for a lunar rover, the astronauts would traverse on foot, using enhanced moon suits that would stretch their range to around 2.5 kilometers. There would be three traverses in all.
The first would have one astronaut setting up an Apollo Lunar Scientific Experiment Package (ALSEP) just over a kilometer east of the lunar module. The other astronaut would walk along a low ridge visible from the Surveyor 7 and sample boulders there. Then the two astronauts would meet up and take samples from nearby the lunar module at “flow dome material.”
The second traverse would have taken the astronauts to a dark “lake” that had once consisted of molten rock to take samples. They would also visit the Surveyor 7 to take samples of materials and parts of the robotic lander.
The third traverse would have taken the astronauts to a number of geologically interesting sites, including another dark “lake,” and an impact crater.
NASA engineers would eventually veto Tycho as a landing site, over the objections of the geologists. The ground was too rugged and the site too far from the easy to access lunar equatorial region that the other Apollo missions landed in. Thus Tycho, though often imaged from above, remains unvisited by human beings to this day.