The Sahara is the world’s largest hot desert and one of the harshest environments on the planet. It is third largest desert overall after Antarctica and the Arctic, which are cold deserts.
At 3.6 million square miles (9.4 million square kilometers), the Sahara, which is Arabic for "The Great Desert," engulfs most of North Africa. The desert covers large sections of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan and Tunisia
Many people imagine the Sahara as dotted with sand dunes, and the desert does have its share of ergs, which are large areas of shifting sand dunes, with some of some of them reaching 590 feet (180 meters). However, most of the Sahara is characterized as rocky hamada, a type of desert landscape that has very little sand and is made up of primarily barren, hard, rocky plateaus.
With the exception of the Nile River, the Sahara’s rivers and streams are irregular or seasonal. The Nile crosses the desert from its origins in central Africa to empty into the Mediterranean.
The central part of the Sahara has extremely limited vegetation. The northern and southern reaches of the desert, along with the highlands, have areas of sparse grassland and desert shrub, with trees and taller shrubs.The Sahara has mesmerized outsiders for centuries. The world's largest desert, its size defies imagination: 3.3 million square miles or around 25 percent of Africa. Not surprisingly, the Sahara's name in Arabic means simply "desert."

Camel caravans looking for gold, ivory, grain, salt and slaves made the Sahara the world's first gateway to Africa. These endless trains, run by Tuaregs, Arabs and others, gave rise to the legendary era of trans-Saharan trade, a phenomenon that still defines the Sahara to many outsiders.

Today, the Sahara still serves as a border between the continent's black African south and Arab-influenced north. Its scorching heat and size still influence the cycle of drought and rainfall in sub-Saharan Africa. With one of the planet's lowest population densities, its people -- Tuareg, Arab, Tubu, Moor - can seem afloat in vast seas of sand. Blue-robed Tuaregs still run salt caravans and herd goat, sheep and camels. Moors farm date palms.
Another common feature in the desert is rocks. Plateaus contain large boulders, and full-blown mountains are not uncommon (and get lots of snow in the winter). Some mountains are volcanic as well and are a mix of live and dormant.

Grasses, trees, and plants can be found in the Sahara, although nearly all species are hearty, drought-resistant survivors. Animals can be plentiful, including hundreds of species of reptiles and mammals. The number of species of birds alone tops 300. Many of those species are migratory, however, able to move quickly to a new home if their water supply literally dries up.
As for people, not surprisingly, the Sahara Desert has one of the lowest population densities on the planet. In the 3.5 million square miles of sands, mountains, and waterways live just 2.5 million people. Obviously, the population is the largest near lakes and rivers. Even so, the majority of the people are nomads.

The climate of the Sahara has gradually gotten harsher. Archaeological remains point to water sources much more widely available and a population much more spread out.
The Sahara's desert climate is believed to have been established over five million years ago during the Pliocene Epoch. Since then the Sahara has been subject to short- to medium-length dry and humid conditions, which have contributed to the unique climate of the Sahara today. For the past 2,000 years, the climate of the Sahara has remained quite consistent, except for a period of time in the 16th and 18th century when there was a "Little Ice Age" in Europe. This ice age significantly increased the amount of precipitation over the whole Sahara Desert until around the 19th century. By this time, the climate had become quite stable again and resembled the desert climate of today.
The Sahara's climate consists of basically two sub-climates, a dry subtropical climate in the north and a dry tropical climate in the south. The dry tropical climate is generally characterized by mild, dry winters, a hot dry season just before the rainy season, and an annual temperature cycle. The dry subtropical climate, however, is characterized by annually high temperature ranges, cold winters, hot summers and two rainy seasons. There is a narrow strip in the western portion of the Sahara, along the coast, which generally has cool temperatures compared to the rest of the Sahara because of the influence of the cold Canary Current.

Salar de Uyuni Background

Salar de Uyuni comprises over 10,000 sq km in the Potosi region. The salt is over 10 meters thick in the center. In the dry season, the salt planes are a completely flat expanse of dry salt, but in the wet season, it is covered with a thin sheet of water that is still drivable.
The standard tour heads south toward the southwest corner of Bolivia, by many fluorescent-colored lakes that are created from a collection of different minerals from runoff from the surrounding mountains.

The world's largest salt flat sits at a lofty 3653m (11,985ft) and blankets an amazing 12,000 sq km (4633 sq mi). It was part of a prehistoric salt lake, Lago Minchín, which once covered most of southwest Bolivia. When it dried up, it left a couple of seasonal puddles and several salt pans, including the Salar de Uyuni. The savage beauty of this vast salt desert makes it one of South America's most awe-inspiring spectacles.
From strange islands in a sea of blindingly bright salt to delicately colored mineral lakes in the Andean mountains, this is an unforgettable Bolivian landscape.
However, travellers should take great care in choosing which tour operator to go with when visiting the salt flats. Fatal accidents due to unsafe vehicles and drivers are not unheard of. Make sure your vehicles have seatbelts, emergency radio transmitters and first aid equipment, and don't shy from asking about guides' levels of training and experience. Of course, there are also many reputable tour operators in the area who will ensure your experience of this natural wonder is both memorable and safe.
3,800 square-miles of salt flat spread out across Bolivia's remote southwest. Salar de Uyuni is the largest salt flat in the world, an endless sheet of hexagonal tiles (created by the crystalline nature of the salt), dotted with pyramids of salt. Despite the desert dryness, freezing night temperatures, and fierce desert sun, this landscape is not devoid of life. Pink flamingos, ancient cacti, and rare hummingbirds all live in the Salar de Uyuni.
During the wet season, the salt desert is transformed into a enormous salt lake, albeit one that is only six to twenty inches deep, traversable by both boat and truck. During this time, the shallow salt lake perfectly mirrors the sky, creating bizarre illusions of infinity. In the middle of this seemingly infinite salty lake is a hotel built entirely out of—naturally—salt.
Created from salt bricks held together with salt mortar, the hotel and everything inside it, including the chairs and tables, is made from salt. While the Hotel Playa Blanca has no electricity and little in the way of amenities, and its water must be trucked in, it does offer even more important and certainly rarer qualities: utter silence, an all-encompassing austere beauty, and an astonishing view of the night sky.
Also worth traveling to are the nearby Laguna Colorado and Laguna Verde. Laguna Colorado is a red-hued lake filled with thousands of pink flamingos, while Laguna Verde is a blue-green salt lake found at the foot of the volcano Licancabur. Its shifting aqua color is caused by copper sediments and microorganisms living within the lake.

The town of Riomaggiore presents typical features reflecting its history and traditions.
The town stretches along a vertical axe where steep staircases are the only means to move around the town.
The typical houses have one or two-floor towers in order to use at best the place at disposal.
The first historical traces date back to 1239, when the inhabitants of the feudal district of Carpena entered in the Compagnia Genovese.
Only in 1343 Riomaggiore became independent as municipality and administration, and during Napoleon’s age it absorbed also the town of Manarola, whose historical roots are even older than Riomaggiore itself.
Guardiola Tower, now a natural park, once it was one of the most equipped fortresses in the area.
The church of san Giovanni Battista dates back to 1341, and its façade was rebuilt in neogothic style in 1820. Also the parish church of san Lorenzo dating back to 1338 has a gothic façade.
The castle of Riomaggiore (15th-16th Century) rises on a rocky crag dividing the most ancient part of the town from the one standing nearby the railway station. Among the personalities who were born in Riomaggiore there is the painter Telemaco Signorini.

Not far from a group of houses, on the hill of Cerricò, you can find the castle, a fortification dating back to the 13th Century e from where you can enjoy a wonderful sight over the sea.

In the highest part of the town there is the parish church of san Giovanni Battista built in 1340 by the bishop of Luni, Antonio Fieschi. Going down along the road of the Sanctuary you can reach the oratory “dei Disciplinati” (16th Century), very interesting for the paintings in its interior. About 350 metres from the sea, along the coast road connecting the Cinque Terre with La Spezia, you can find the sanctuary of Madonna di Montenero.

About Guardiola Tower, reachable through a footpath leaving from town, we can tell that is the best beauty spot overlooking the coast and the town. Very interesting is the Environmental Education Centre of Torre Guardiola, whose aim is organizing several events for nature lovers of all ages. Among them there is the “Writing Trail”, which, through some laps indicated by panels, invites the tourists to express their creativity by writing poems about the beauty of the landscape.

Castle of Riomaggiore: you can reach the fortification from the town, climbing the steep road from the railway station. It began to be built in 1260 by the Marquis Turcotti, lord of Ripalta and feudal vassal of this part of the coast, who gave up all these properties to Nicolò Fieschi who, after some years, transferred them to the Republic of Genoa, which completed the defensive system of Riomaggiore. The castle has a square base with the longest sides overlooking the sea. The boundary wall has two circular towers. The entrance is located between the towers, and a narrow external stair leads to the tower controlling the town, where a big clock is built. Not far from it there is the oratory of San Rocco, built in remembrance of a plague which stroke the community in 1480. During the times the castle suffered not only the usual wear of atmospherical agents but also a modification which changed the original setting up. In fact, until few years ago, the internal part of the fortress housed the town cemetery.
The Cinque Terre, are five small villages on the "Costa Ligure of Levante". The villages from north to south are: Monterosso al Mare, Vernazza, Corniglia, Manarola, and Riomaggiore. Since 1926, the Cinque Terre towns have been part of the province of La Spezia.
This territory was long isolated and the characteristic Ligurian culture has been conserved. The five villages were only reached by the outside world about one hundred years ago, when the railway line was built.

The chain of mountains that surrounds these villages runs parallel to the "Appennino Mountains" and creates small insenature, steep valleys where the towns are situated. This makes for a unique landscape, different from the rest of the coast. Right in the center of this landscape during the centuries was placed the man Ligure, always in struggle and always in love with its territory. The result of this geography is the typical houses liguri, the narrow bands and the knoll in terrace built on the rocks.

The Cinque Terre is a National Park and territory protected by UNESCO. This zone is characterised by the presence of typical steep slopes cultivated with vines thanks to terraces, unique witness of the transformation of the territory carried out by mans hard work.The suggestive kind of coast falling sheer to the sea, with cliffs which are often vertical, alternated with small creeks and enchanting beaches among rocks, with depths rich in fish, make this territory a real Natural "work of art".