Once upon a time, there was the city of Tiwanaku or Tiahuanaco, the capital of a powerful pre-Inca civilization, located near the southern shore of Lake Titicaca in Bolivia between 500 and 900 AD. However, the name by which Tiwanaku was known to its inhabitants is still unknown, as they had no script or written language. Nevertheless, from the available archaeological remains it is concluded that there was a time between that specified period when the cultural and political influence of the city of Tiwanaku was stretched from northern Bolivia to the Peruvian coast in the north and even in parts of northern Chile in the south. Due to the absence of any script, the inhabitants of the city were not in a position to leave any written history of their own, but it is considered that the important constructions of the city began around 700 AD and the city steadily flourished for next few centuries. During its prime time the city of Tiwanaku covered an estimated area of around 2.6 km of land and was the home of 20 000 inhabitants and though it faded to obscurity by 1200 AD, its culture lived on through its religious influence over the Incas. However, the Incas strongly believed that the city was neither built by man, nor by any earlier civilization, it was created by their almighty god Viracoca, who rose from the depths of Lake Titicaca. They believed Tiwanaku to be the site where the world was created.

The archaeological site of the ancient city contains lots of excavated structures, among which Akapana pyramid, Akapana East, the Kalasasaya, the stepped platforms of Pumapunku, the Kheri Kala, the Putuni enclosures and the Semi-Subterranean temple are considered as important. It is theorized that the Pumapunku complex, along with the Akapana pyramid and the other structures jointly functioned as the spiritual and ritual centers for the Tiwanaku.

However, considered as one of the biggest pre-Columbian constructions in South America and a structure of great spiritual significance for the Tiwanaku civilization, the Akapana pyramid is perhaps the most outstanding among all the structures on the site. Initially, it was thought to be developed from a modified hill. But the later studies in the Twenty-first-century studies have shown that it is an entirely man-made earthen mound, faced with a mixture of large and small stone blocks. The 843 feet (257 m) wide and 646 feet (197 m) broad, almost cross-shaped pyramidal structure with seven superimposed platforms and stone retaining walls rose to a height of over 59 feet (18 m).

Equipped with a sculptured staircase on its western side, the centre of its flat summit appears to be a sunken court, which is generally attributed to the indiscriminate digging by the early Spanish looters, who used the unprotected pyramid as a stone quarry. It is estimated that the structure was once surmounted by a temple. There are many carved stone heads set into the walls of the small semi-subterranean temple, symbolizing an earlier practice of exposing the severed heads of defeated enemies in the temple. There is a large stone block within the Akapana, weighing approximately 65.70 metric tons, which was once possibly used in shamanic rituals and probably a High Priest was buried there with a puma effigy incense burner. Puma-headed human iconography also covers the stonework of the temple.

The Akapana East, made of a thick, prepared floor of sand and clay, was built on the eastern side of early Tiwanaku and is considered a boundary between the ceremonial center and the urban area. Probably to enhance the aesthetic beauty, Yellow and red clay were used in different areas of it.

The Pumpapunku or the Gateway of the Puma, located one mile to the south-west of the main complex, is a terraced earthen mound, faced with blocks. In fact, it is a part of a large temple complex or a part of a monument group that consists of an unwalled western court and a central esplanade, a terraced platform mound faced with stone and a walled eastern court. For the construction of the wall, each stone was finely cut to interlock with the surrounding stones and the blocks were fitted together like a puzzle, forming load-bearing joints without the use of mortar. Its eastern edge was occupied by a stone terrace called the Pltaforma Litica, paved with multiple enormous stone blocks. It contains the largest stone slab found in the area, which is estimated to weigh about 131 short tones. It is believed that during its prime time, Pumpapunku was unimaginably wondrous with its polished metal plaques, brightly coloured ceramic and fabric ornamentation.

Located to the north of the Akapana, the Kalasasaya or Stopped Stones that dates to at least 200 BC to 200 AD, is a low platform mound with a large courtyard, which is surrounded by high stone walls. Like the other platform mounds in the area, it also has a central sunken court, which can be reached by a single staircase through an opening in its eastern wall. The sunken court was the space for religious ceremonies, which had tenon heads, stone carving of the heads, protruding from the interior of its sandstone perimeter walls which also include the regularly placed tall columns. The single staircase leading to the precinct also has stone columns either side. The precinct houses a huge monolith with a height of around 12 feet, known as the Ponce Monolith, perhaps depicting a god or a High Priest or a ruler of Tiwanaku

Located in the north-west corner of the Kalasasaya, the massive Puerta del Sol or the Gateway of the Sun, carved from a single massive block of andesite stone, is one of the most famous structures of Tiwanaku. The top portion of the gateway is decorated with relief carvings of 48 winged demons or angels, each with either a human or bird head and wearing a feathered headdress. Interestingly, many researchers have interpreted the gateway to be a solar-lunar calendar with similarities to later Aymara and Inca traditions. A look alike, but smaller gateway, carved with animal designs, is located near the western end of Kalasasaya, which is known as the Puerta de la Luna or the Gateway of the Moon.

Made of red sandstone, the Semi-Subterranean temple is located in the east of the main entrance of the Kalasasaya. It also has a sunken court which can be accessed by a single staircase leading down into the court from the south side. The interior wall of this court also has stone heads protruding from it.

Possibly, the city of Tiwanaku was abandoned as late as 1100 AD, due to excessive drought and shortly after its fall, the site became the victim of indiscriminate looting and amateur excavations. Except the public and the non-domestic foundations with poorly reconstructed walls, no other buildings have survived at the modern site. Although the main Tiwanaku site was enlisted in the UNESCO World Heritage Site in 2000, currently the site, spreading around 4 square kilometers, includes only the decorated ceramics, dilapidated structures and the megalithic blocks.

The Bolivian government initiated an effort to restore the site in the 1960s and reconstructed some parts of it. In fact, the walls of the Kalasasaya are almost all reconstructed, but the reconstruction was not sufficiently based on research. Even the Gateway of the Sun, now in the Kalasasaya, is believed to have been moved from its original location.