Leaning Tower of Pisa

The Leaning Tower of Pisa (Italian: Torre pendente di Pisa) or simply The Tower of Pisa (La Torre di Pisa) is the campanile, or freestanding bell tower, of the cathedral of the Italian city of Pisa. It is situated behind the Cathedral and it is the third structure by time in Pisa's Piazza del Duomo (Cathedral Square).
Although intended to stand vertically, the tower began leaning to the southeast soon after the onset of construction in 1173 due to a poorly laid foundation and loose substrate that has allowed the foundation to shift direction.
The height of the tower is 55.86 m (183.27 ft) from the ground on the lowest side and 56.70 m (186.02 ft) on the highest side. The width of the walls at the base is 4.09 m (13.42 ft) and at the top 2.48 m (8.14 ft). Its weight is estimated at 14,500 tonnes. The tower has 296 steps (the seventh floor has a different number of steps on the two sides, if you climb it on the north part you can count only 294 steps). The tower leans at an angle of 3.97 degrees. This means that the top of the tower is 3.9 meters from where it would stand if the tower were perfectly vertical.
Due to the peculiarity of the tower, there is no lift inside, on the contrary of common belief.

Hagia Sophia

Hagia Sophia (Greek: Ἁγία Σοφία; "Holy Wisdom", Turkish: Ayasofya) is a former patriarchal basilica, later a mosque, now a museum, in Istanbul, Turkey. Famous in particular for its massive dome, it is considered the epitome of Byzantine architecture. It was the largest cathedral in the world for nearly a thousand years, until the completion of the Medieval Seville Cathedral in 1520.
The current building was originally constructed as a church between 532 and 537 AD on the orders of the Byzantine Emperor Justinian, and was in fact the third Church of the Holy Wisdom to occupy the site (the previous two had both been destroyed by riots). It was designed by two architects, Isidore of Miletus and Anthemius of Tralles. The Church contained a large collection of holy relics and featured, among other things, a 50 ft (15 m) silver iconostasis. It was the patriarchal church of the Patriarch of Constantinople and the religious focus point of the Eastern Orthodox Church for nearly 1000 years.
In 1453, Constantinople was conquered by the Ottoman Turks and Sultan Mehmed II ordered the building to be converted into a mosque. The bells, altar, iconostasis, and sacrificial vessels were removed, and many of the mosaics were eventually plastered over. The Islamic features - such as the mihrab, the minbar, and the four minarets outside - were added over the course of its history under the Ottomans. It remained as a mosque until 1935, when it was converted into a museum by the secular Republic of Turkey.
For almost 500 years the principal mosque of Istanbul, Hagia Sophia served as a model for many of the Ottoman mosques such as the Sultan Ahmed Mosque (Blue Mosque of Istanbul), the Şehzade Mosque, the Süleymaniye Mosque, and the Rüstem Pasha Mosque.
Although it is sometimes referred to as Saint Sophia (Greek for wisdom), the Greek name in full is Church of the Holy Wisdom of God Ναός τῆς Ἁγίας τοῦ Θεοῦ Σοφίας - and it was dedicated to the Holy Wisdom of God rather than a specific saint named Sophia

Porcelain Tower of Nanjing

The Porcelain Tower (or Porcelain Pagoda) of Nanjing (Chinese: 南京陶塔; pinyin: Nánjīng Táotǎ), also known as Bao'ensi (meaning "Temple of Gratitude"), is a historical archaeological site located on the south bank of the Yangtze in Nanjing, China. It was constructed in the 15th century as a Buddhist pagoda, but was mostly destroyed in the 19th century during the course of the Taiping rebellion. However, the tower is now under reconstruction once again.

Great Wall of China

The Great Wall of China (simplified Chinese: 长城; traditional Chinese: 長城; pinyin: Chángchéng; literally "Long wall") or (simplified Chinese: 万里长城; traditional Chinese: 萬里長城; pinyin: Wànlǐ Chángchéng; literally "The long wall of 10,000 Li (里)") is a series of stone and earthen fortifications in China, built, rebuilt, and maintained between the 5th century BC and the 16th century to protect the northern borders of the Chinese Empire during the rule of successive dynasties. Several walls, referred to as the Great Wall of China, were built since the 5th century BC. The most famous is the wall built between 220 BC and 200 BC by the first Emperor of China, Qin Shi Huang; little of it remains; it was much farther north than the current wall, which was built during the Ming Dynasty.
The Great Wall is the world's longest human-made structure, stretching over approximately 6,500 km (4,000 miles) from Shanhaiguan in the east to Lop Nur in the west, along an arc that roughly delineates the southern edge of Inner Mongolia, but stretches to over 6,700 km (4,160 miles) in total. It is also the largest human-made structure ever built in terms of surface area and mass. At its peak, the Ming Wall was guarded by more than one million men. It has been estimated that somewhere in the range of 2 to 3 million Chinese died as part of the centuries-long project of building the wall.

The Catacombs of Kom el Shaqafa

The Catacombs of Kom el Shaqafa (meaning 'Mound of shards' or 'Potsherds') is a historical archaeological site located in Alexandria, Egypt. The necropolis consists of a series of Alexandrian tombs, statues and archaeological objects of the Pharaonic funeral cult with Hellenistic and early Imperial Roman influences. Due to the time period, many of the features of the Catacombs of Kom el Shoqafa merge both Roman, Greek and Egyptian cultural points; some statues are Egyptian in style, yet bear Roman clothes and hair style whilst other features share a similar style. A circular staircase, which was often used to transport deceased bodies down the middle of it, leads down into the tombs that were tunneled into the bedrock during the age of the Antonine emperors (2nd century AD). The facility was then used as a burial chamber from the 2nd century to the 4th century, before being rediscovered in 1900 when a donkey accidentally fell into the access shaft. To date, three sarcophagi have been found, along with other human and animal remains which were added later. It is believed that the catacombs were only intended for a single family, but it is unclear why the site was expanded in order to house numerous other individuals. The Catacombs of Kom el Shoqafa is, according to some lists, also one of the Seven Wonders of the World in the Middle Ages. One of the more gruesome features of the catacombs is the so called Hall of Caracalla. According to tradition, this is a mass burial chamber for the humans and animals massacred by order of the Emperor Caracalla.

Colosseum

The Colosseum or Coliseum, originally the Flavian Amphitheatre (Latin: Amphitheatrum Flavium, Italian Anfiteatro Flavio or Colosseo), is an elliptical amphitheatre in the centre of the city of Rome, Italy, the largest ever built in the Roman Empire. It is one of the greatest works of Roman architecture and engineering.
Occupying a site just east of the Roman Forum, its construction started between 70 and 72 AD under the emperor Vespasian and was completed in 80 AD under Titus, with further modifications being made during Domitian's reign (81–96). The name "Amphitheatrum Flavium" derives from both Vespasian's and Titus' family name ("Flavius, from the gens Flavia).
Originally capable of seating around 50,000 spectators, the Colosseum was used for gladiatorial contests and public spectacles. It remained in use for nearly 500 years with the last recorded games being held there as late as the 6th century. As well as the traditional gladiatorial games, many other public spectacles were held there, such as mock sea battles, animal hunts, executions, re-enactments of famous battles, and dramas based on Classical mythology. The building eventually ceased to be used for entertainment in the early medieval era. It was later reused for such varied purposes as housing, workshops, quarters for a religious order, a fortress, a quarry and a Christian shrine.
Although it is now in a ruined condition due to damage caused by earthquakes and stone-robbers, the Colosseum has long been seen as an iconic symbol of Imperial Rome. Today it is one of modern Rome's most popular tourist attractions and still has close connections with the Roman Catholic Church, as each Good Friday the Pope leads a torchlit "Way of the Cross" procession to the amphitheatre.
The Colosseum is also depicted on the Italian version of the five-cent euro coin.

Stonehenge

Stonehenge is a prehistoric monument located in the English county of Wiltshire, about 8 miles (13 km) north of Salisbury. One of the most famous prehistoric sites in the world, Stonehenge is composed of earthworks surrounding a circular setting of large standing stones. Archaeologists believe that the standing stones were erected around 2200 BC and the surrounding circular earth bank and ditch, which constitute the earliest phase of the monument, have been dated to about 3100 BC. The site and its surroundings were added to the UNESCO's list of World Heritage Sites in 1986 in a co-listing with Avebury henge monument, and it is also a legally protected Scheduled Ancient Monument. Stonehenge itself is owned by the Crown and managed by English Heritage while the surrounding land is owned by the National Trust.