A view of sculptures in Khalid Nabid Cemetery in 2010. Many of them have since disappeared.
Located in the green hills of northeast Iran, the Khalid Nabi Cemetery, also known as the “Valley of Genitalia”, is a historic site famous for its very phallic sculptures, thought by some to be gravestones. Recently, however, visitors have noticed that many of them have gone missing.
Our Observer, who works in the tourism industry, says that about half of the original 600 sculptures have vanished in the last few of years.
A fallen sculpture. 
Not much is known about these phallic sculptures, located 90 kilometres from the city of Gonbad-e Qabus. According to the only archaeological study conducted, the oldest sculptures dates back about 1,000 years; others were sculpted 500 years ago, during the Islamic medieval era. The most recent one is only 70 years old.
Sculptures in 2010.
Some archaeologists believe that this site was established as a cemetery by a group of inhabitants of the region who worshipped phallic symbols a millennium ago.
According to a legend locals still tell today, Khalid Nabi, a prophet also known as Khalid bin Sinan, was being chased by apostates on this very site long ago. He asked God to turn them into stone – that is, into these sculptures. Khalid Nabi then died, and as legend has it, was buried in a mausoleum located just next to the cemetery.

“There are also rounder sculptures resembling female breasts, believed to mark the burial sites of women”

Ramin (not his real name) has worked in Iran’s tourism industry for years. He has travelled to Khalid Nabi Cemetery on several occasions.
The cemetery site is unrelated to the prophet Khalid Nabi, but got its name due to its proximity to the mausoleum. While experts aren’t certain it is in fact a cemetery, as it’s never been excavated, it seems likely, since there are several smaller cemeteries in Iran that include phallic gravestones.
The sculptures, which are of different sizes and shapes, are each carved from single rocks. There are three different types. First, there are the vertical, cylindrical ones resembling phalluses. Second, there are rounder ones that resemble human breasts. Thirdly, there are animal heads, mainly rams’ heads. Iranian archaeologists believe they mark the burial sites of men, women, and prominent tribal figures, respectively. [Scottish archaeologist David Stronach, an Iran specialist, has provided an alternative theory: he has posited that these sculptures are highly stylized representations of human figures.]
Some archeologists believe this type of sculture was used for women's burials. 
I have visited this site three times. My last visit was in August; I hadn’t been back in three years. I noticed that the number of gravestones had been noticeably reduced. While I don’t have exact figures, I would estimate that their number was halved.
A photo of the cemetary taken by our Observer in August 2013. Many of the sculptures that once dotted this hillside have disappeared. The hills' grass is scorched in the summer months. 
“Sadly, tourists are not always respectful of the site”
Three years before, me and the tourists I had brought to the site posed for pictures in front of the tallest sculpture, which was nearly three metres high. But in August, it was gone. There are lots of holes that clearly show where the recently-vanished columns were located.
Sculptures in 2010.
Given the increase in tourists from all over Iran who have visited the cemetery in recent years, I suspect that some locals may have good reason to want these sculptures to disappear. After all, they’re located right next to the mausoleum, and the tourists are distracting to the believers who worship there. Sadly, tourists are not always respectful of the site. And locals do not realize the potential benefits of developing the tourism sector in the region. The authorities, meanwhile, seem to have no interest in either developing or preserving this historic site. Though it has been declared a national heritage site, there is just a metal shack where they sometimes sell tickets during peak tourism season, in the spring. There are no fences nor guards to deter thieves.
Our Observer and a group of tourists posed for this photo three years ago. He says this particularly tall sculpture has since vanished.
Another tall sculpture that our Observer says has vanished. (Photo taken three years ago).