In pics: Part of the Great Wall of China most tourists never see

But the unrestored section between Jinshanling and Simitai is far less travelled.

The wall, at 5,500 miles, is actually a series of fortifications built as early as the 7th century BC that were eventually joined by a continuous path.

Sections of the wall have been built and rebuilt, while others have disappeared altogether.

When Rindge and Nataki visited on a sweltering June day, they saw no more than 30 hikers in an 8 or 9-hour period.

Splendid isolation.

One of the fortifications on the Wall.

The major fort at Simitai.

There were just a few unarmed and visible guards during the couple's hike on the wall.

Apart from the heat, the biggest challenge was climbing on the crumbling stones, which have stood for thousands of years.

"Parts of the wall were easy to walk, but many of the sections not only had rock that was crumbling, but had very steep inclines", Rindge said.

"There were sections where you literally had to walk on all fours because of the condition of the rock and the incline."

"The rock/brick had eroded so much in some places and crumbled in others," said Nataki. "Long stretches felt like rock climbing horizontally - searching for toe holds and finger holds, at one point grabbing onto weeds and praying they would hold."

While parts of the Wall have been renovated, much of it lies in disrepair.

In some places, locals have taken stones to build their own homes.

Other parts have been destroyed to make way for construction projects.

Apart from fellow hikers and the occasional guard, there are also locals selling water and snacks along the route.

Naturally, the vendors on the Wall charge inflated prices - partly because they are selling to a captive audience; partly because of the effort involved in getting goods up the steep climb.

Spectacular.

The vendors use watchtowers spread out along the route to store their goods.

But since they were unrestored, even the watchtowers could be perilous. At one point, a wall had crumbled and given way to a steep drop.

Due to safety concerns, the section of the wall that Rindge and Nataki hiked has been closed since June 2011.

But it's expected to reopen sometime soon.