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This photo was taken from the John Muir Trail on Mount Whitney, the tallest peak in the continental United States at 14,505 feet. A hiker in good shape can make it to the top and back in a single day, though it's quite a trek—it can take 12-18 hours to complete.Photo: Gary C. Tognoni/Shutterstock

The San Francisco Bay is one of the most populous regions in the US—and one of the most beautiful. Its most famous landmark is the Golden Gate Bridge, along with tourist areas like Fisherman’s Wharf and the former prison on Alcatraz Island. The city itself is a cultural hub in the region, as are San Jose and Oakland, the two next largest cities after SF. And of course, there's the fog.Photo: IM_photo/Shutterstock

Death Valley contains the lowest elevation in North America and holds the world record for the highest measured air temperature. And it's staggeringly beautiful at sunrise. A relatively quick drive from the Inland Empire region, it's also close to Sequoia National Park—a totally different biozone. Death Valley is part of the larger Great Basin, and is just to the east of the Sierra Nevada Mountains. The lowest point in North America is at Badwater Basin, and Furnace Creek in Death Valley consistently has the highest temperatures in the United States.Photo: Joanne Dale/Shutterstock

Only 75 km long, the river, however, passes some incredible sites, while it stretches from its source to Lake Tjaktjajaure. The most famous part of the river is the Laitaure Delta at the mouth of the lake. The river also flows through the Rapa Valley, which is surrounded by high mountains and also provides some incredible views.

The river has carved an impressive gorge, which is found a few kilometers from town of Bled, which is famous for its beautiful lake. The wonderful gorge features a wooden hiking trail and bridges that run along the river, enabling to explore the site. The pathway ends at the stunning point – the picturesque waterfall Šum marks the finish line. The route offers an exhilarating walk on a hot summer day.

Only a 120 km (75 mi) long tributary of the Snake River, the Gros Ventre, however, mesmerizes with beautiful surroundings. It mostly passes the Gros Ventre Wilderness, which is famous for its unspoiled nature. The river is a popular site among the fishermen, who come to catch huge trouts. Horseback riding and kayaking are other favorite activities here, as well as hiking.

Also known as the River of Five Colors, Caño Cristales is the most spectacular natural wonder in the country. Found in the mountain range of Serranía de la Macarena, the river mesmerizes with amazing colors: vivacious yellow, green, blue, black and red shades quiver from the bottom. It is a result of a red plant – Macarenia clavigera – growing in the riverbed. Other colors come from black rocks, green algae, blue water and yellow sand, producing an iridescent effect.

Flowing through mountains and valleys, and villages, and cities – rivers have been attracting settlers to build the civilizations around them for centuries. Today a lot of them attract tourists, who love to participate in the outdoor activities. Check out these ten choices we have this week.

Conwy Castle was built between 1283 and 1289 during King Edward I’s second campaign in North Wales. Six years later the castle was besieged by the last native Prince of Wales. The siege lasted for several months and supplies ran low. However the castle and town were not captured. An estimated £15,000 (the equivalent of £162 million in 2009) was spent building the castle and the town’s defences. The cost of all of his five major castles in Wales was around £60,000. The total cost to Edward for his Welsh campaigns and castle building was in the region of a third of a million pounds. More than ten times his annual income.

Qasr Kharana is one of the best-known of the desert castles located in present-day eastern Jordan. Built sometime before the early 8th century, it is one of the earliest examples of Islamic architecture in the region. Having a limited water supply it is probable that Qasr Kharana sustained only temporary usage and there are different theories concerning the function of the castle, it may have been a fortress or a meeting place for Bedouins.

The Giza necropolis, situated in the immediate vicinity of the southwestern suburbs of Cairo is probably the most famous ancient site in the world. The pyramids in Giza were built over the span of three generations – by Khufu, his second reigning son Khafre, and Menkaure. The Great Pyramid of Khufu is the oldest and sole remnant of the Seven Wonders of the Ancient World. Over 2 million blocks of stone were used to construct the pyramid, during a 20 year period concluding around 2560 BC. The pyramid is an awe-inspiring 139 meters (455 feet) high making it the largest pyramid in Egypt, although nearby Khafre’s Pyramid appears to be larger as it is build at a higher elevation.

The Great Wall of China built, rebuilt, and maintained between the 5th century BC and the 16th century to protect the northern borders of the Chinese Empire from the attacks of the Xiongnu tribes. Several walls have been built that were referred to as the Great Wall. One of the most famous is the wall built between 220–206 BC by the first Emperor of China but little of that wall remains. The majority of the existing wall were built during the Ming Dynasty (1368-1644 AD). The most comprehensive archaeological survey has recently concluded that the entire Great Wall, with all of its branches, stretches for 8,851.8 kilometers (5,500.3 miles).