Why do so many of us feel drawn by the idea of travel to sacred sites? Uluru, Easter Island, the Camino, Stonehenge, the Mayan ruins... Have you never wondered about their mysteries or their origins?
Most are shrouded in secrecy, their original meanings hidden in time.
Some are man-made and some are natural but each has a significance far beyond what we can see and it is precisely this mystique that attracts so many of us.
Whatever our reasons for wanting to visit, these sites exert their magic on us, bringing us something extra, something often undefined, supernatural, divine. Something... intuitive.
There are thousands of sacred places and it would also take thousands of pages to list them all.
Perhaps these will whet your appetite for this kind of slow, meaningful travel - and perhaps you'll add a few of your own to this list.
In Europe, most sacred sites are of the human-made variety - abbeys, monuments, temples or shrines...
One of the continent's greatest unexplained sites is England's Stonehenge, believed to be more than 5000 years old.
It's impressive up close, yet no one knows why it was built.
There's speculation it could be for astronomy or a computer or an alien spaceship docking station or related to human sacrifice. The most recent theory is that it is a giant female sexual organ - a symbol of fertility. Unfortunately, the stones are closed to the general public - you can only walk around the perimeter except once a year during Summer Solstice, when people are allowed close up.
But you can walk through the stones of Avebury Henge, Britain's largest prehistoric stone circle, and even touch them. It's far less touristy than its neighbor and pretty much as old. Many visitors believe it is the best of the two, although purists know many of the stones have been moved from their original places.
One of my favorite sacred European sites is the Benedictine Abbey on top of the tiny island of Mont-Saint-Michel, off the coast of Normandy in France (and not to be confused with St Michael's Mount in Cornwall, a similar site across the English Channel).
According to legend, the monastery was built on the orders of the Archangel Michael - as was the English site, hence their common name.
But beware. The tides are treacherous between the island and the Normandy coast. When they come in, they are faster than you can run. So, no matter how tempting, take the causeway.
People still die because the seabed crossing looks so peaceful at low tide.
A sacred site doesn't have to be an endpoint or a destination - it can be a long-distance journey, like a pilgrimage to Santiago, all the way to the sacred site of Santiago Cathedral, which houses the relics of St. James (Santiago in Spanish) as well as pieces of what is believed to be the True Cross.
Look for the shell on the altar - pilgrims kiss it as a sign of devotion - and gratitude at the end of their grueling journey on foot.
Some travel to sacred sites is off-limits to women.
Don't try to go to Mount Athos, a Greek Orthodox monastery that sits on a peninsula in Thessaloniki. Not only have women been barred from it for nearly a thousand years, but even female domestic animals aren't allowed.
On the other hand, the Flemish Béguinages are building clusters - churches, houses, gardens - created for communities of Flemish nuns. They were founded 800 years ago by women dedicated to God but who were not cloistered. They represent the unusual culture of northwestern Europe's independent religious women, and are classified by UNESCO as a World Heritage Site.
And that doesn't even begin to scratch the surface of churches, basilicas, cathedrals and abbeys that populate every corner of the continent.
Europe also has its share of natural sacred sites.
Each year, up to a million pilgrims climb Mount Croagh Patrick, in County Mayo in Ireland. They walk the stations of the cross and attend Mass.
As in many Catholic pilgrimages, it also serves as penance - in which case the climb takes place barefoot. Around 1 August there is a harvest festival, which was particularly important for women, who slept on the summit to promote fertility.
From Europe to the Middle East, sacred sites dating back to biblical times stretch across the land.
The life of Jesus is rife with tales of sacred sites, most of which are in present-day Israel.
Some of the most famous?
Rachel's Tomb, between Bethlehem and Jerusalem, is an important Jewish pilgrimage site, especially for infertile women. It is the third holiest site in Judaism.
Hagya Sofia in Istanbul is now a museum but acknowledged as one of the world's great buildings. It was once a Mosque, and a Byzantine church before that. Any travel to sacred sites in Istanbul should include both the Blue and the Suleymanye mosques, which continue to attract worshippers.
While this next one is not in the Middle East, this other Christian-Muslim place of worship is related by history: the Mezquita (Spanish for mosque) in Cordoba, in southern Spain. In contrast to Hagya Sofia, the Mezquita was first a mosque and then became a church, and is now Cordoba's main cathedral.
Both of these buildings are extraordinary, whether you are religious or not, simply because they are intricate, magnificent and have withstood the test of history.
Mecca in Saudi Arabia holds the holiest mosque in Islam but is off-limits to non-Muslims and open to women only if they are accompanied by a man. Other notable Muslim sites include the Al-Aqsa Mosque and the Dome of the Rock in Jerusalem.
The region is also dotted with natural sacred sites, provided by nature rather than our own hand, like these four sacred mountains of the Judeo-Christian tradition:
Travel to sacred sites in the Middle East should include Mount Nebo in Jordan, overlooking the River Jordan and the Holy Land, mentioned in both the Torah and the Bible and possibly the site from which Moses viewed the Promised Land. Pope John Paul II visited Mount Nebo during his pilgrimage to the Holy Land and planted a peace symbol - an olive tree - on its mountainside.
If I could just take a detour through the African Sahel there is one sacred site I would love to see, and that is the unusual Great Mosque of Djenne, in Mali, the world's largest mud building. These days it is a little close to the line drawn in the sand by dangerous fundamentalists in Mali's North but travelers have said (in March 2015) they feel perfectly safe there.
Continuing our travels eastward we may reach Mount Kailash in Tibet, sacred to Hindus, Jains and Tibetan Buddhists. It is the most respected but least visited sacred mountain because of its ancient and remarkable holiness. It is believed that 108 circuits around the mountain (clockwise or anti-clockwise, depending on your faith) is a direct path to enlightenment, as is a dive into nearby - and also sacred - Lake Manosaravar.
China has two sets of sacred mountains, one linked to Taoism and the other to Buddhism. But perhaps its most sacred mountain is Tai Shan, which is considered a god in itself. The Temple of the Princess, one of two temples at the top, may well be China's foremost women's pilgrimage site.
Travel to sacred sites is easy in Bali, whose most sacred mountain is Gunung Agung. It is still an active volcano that occasionally spews ash, although visitors often climb it. In fact most of Indonesia's volcanoes are sacred in some way, with ceremonies marking the various stages in people's lives.
Mount Fuji, or Fujiyama, is the highest mountain in Japan - you've probably often seen it on postcards, with its perfect snow collar. It is dedicated to the goddess Sengen-Sama, whose shrine is at the summit.
Many people climb Mount Fuji - the first ascent was apparently by an unknown monk in 663 - but it was only opened to women climbers in the early 20th century. The mountain is believed to be the gateway to another world.
In Australia, any travel to sacred sites would begin with Ayer's Rock - more of a rocky plateau than a mountain. It is considered sacred by Aborigines, who call it by its official name, Uluru. While many visitors want to (and do) climb it, the Aboriginal owners ask visitors to respect the rock's sacred nature and to refrain from climbing.
Across the Pacific, Native Americans honor the four sacred mountains of the Navajo:
There are plenty of other Native American sacred mountains, such as Chief Mountain in Montana (sacred for hundreds of years) and Mount Shasta in California, a ritual center not only for Native Americans but for other faiths and some cults as well.
As we well know, Central America is filled with sacred sites.
The Mayan city of Tulum, in additional to being a trading city, was also a pilgrimage site for Mayan women heading towards Cozumel, once a holy island. On Cozumel, the sanctuary of Ix Chel has been paying homage to the Mayan's primary goddess for 800 years.
And then there's travel to Peru - to be more precise, travel to Machu Picchu, the sacred site of Incas. This sacred city is a UNESCO World Heritage Site, the best-preserved city of the former Inca empire, and receives - unfortunately to its detriment - hundreds of thousands of visitors each year.