Stonehenge

Stonehenge is a prehistoric monument located in the English county of Wiltshire, about 2.0 miles (3.2 km) west of Amesbury and 8 miles (13 km) north of Salisbury. One of the most famous sites in the world, Stonehenge is composed of earthworks surrounding a circular setting of large standing stones. It is at the centre of the most dense complex of Neolithic and Bronze Age monuments in England, including several hundred burial mounds.

Archaeologists have believed that the iconic stone monument was erected around 2500 BC, as described in the chronology below. One recent theory however, has suggested that the first stones were not erected until 2400 -2200 BC, whilst another suggests that bluestones may have been erected at the site as early as 3000 BC.

Colosseum

Emperor Vespasian, founder of the Flavian Dynasty, started construction of the Colosseum in AD 72. It was completed in AD 80, the year after Vespasian's death.

Occupying a site just east of the Roman Forum, its construction started in 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's family name (Flavius, from the gens Flavia).

Catacombs of Kom el Shoqafa

The Catacombs of Kom el Shoqafa, is the Arab translation of the ancient Greek name, Lofus Kiramaikos which means "mound of shards" or "potsherds". Located to the southwest of the Pompey’s pillar is a multi level labyrinth featuring dozens of chambers adorned with sculpted pillars, statues and other Romano Egyptian religious symbols, burial niches and sarcophagi as well as a banquet room of Roman style, where memorial meals were conducted by relatives of the deceased.

Great Wall of China

The Great Wall of China is a series of stone and earthen fortifications in northern China, built originally to protect the northern borders of the Chinese Empire against intrusions by various nomadic groups.

Several walls have been built since the 5th century BC that are referred to collectively as the Great Wall, which has been rebuilt and maintained from the 5th century BC through the 16th century. One of the most famous is the wall built between 220-206 BC by the first Emperor of China, Qin Shi Huang. Little of that wall remains; the majority of the existing wall was built during the Ming Dynasty.

Porcelain Tower of Nanjing

The Porcelain Tower (or Porcelain Pagoda) of Nanjing, also known as Bao'ensi meaning "Temple of Gratitude", is a historical site located on the south bank of the Yangtze in Nanjing, China. It was a pagoda constructed in the 15th century during the Ming Dynasty, but was mostly destroyed in the 19th century during the course of the Taiping Rebellion.

There is purportedly a movement underway to reconstruct the tower. As of 2010, reconstruction of the tower and temple grounds went underway. The projected completion date of the first phase of reconstruction is 2014.

Hagia Sophia

Constantine was the first Christian emperor and the founder of the city of Constantinople, which he called "the New Rome." The Hagia Sophia was one of several great churches he built in important cities throughout his empire.

Following the destruction of Constantine's church, a second was built by his son Constantius and the emperor Theodosius the Great. This second church was burned down during the Nika riots of 532, though fragments of it have been excavated and can be seen today.

Hagia Sophia was rebuilt in her present form between 532 and 537 under the personal supervision of Emperor Justinian I.

Leaning Tower of Pisa

The Leaning Tower of Pisa or simply the Tower of Pisa (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 is the third oldest structure in Pisa's Cathedral Square (Piazza del Duomo) after the Cathedral and the Baptistry.

The height of the tower is 55.86 m (183.27 ft) from the ground on the low side and 56.70 m (186.02 ft) on the high 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 metric tons (16,000 short tons).
The tower has 296 or 294 steps; the seventh floor has two fewer steps on the north-facing staircase.
Prior to restoration work performed between 1990 and 2001, the tower leaned at an angle of 5.5 degrees,but the tower now leans at about 3.99 degrees.This means that the top of the tower is displaced horizontally 3.9 metres (12 ft 10 in) from where it would be if the structure were perfectly vertical