Huaca Rajada, also known as Sipán,^[1] is a Moche archaeological site in northern Peru in the Lambayeque Valley, that is famous for the tomb of Lord of Sipán (El Señor de Sipán), excavated by Walter Alva and his wife Susana Meneses beginning in 1987. The city of Sipán is dated from 50–700 AD, the same time as the Moche Period.^[2]

Sipán is an archaeological site where royal tombs were discovered and excavated between 1987–1990,^[3] a fairly recent find in the last 30 years, and is considered to be a very important archaeological discovery. Many of the tombs were looted, yet the artifacts that remained and were discovered by archaeologists play an important role in understanding the Moche rulers and tradition. Tombs have been found also in Sipán's Huaca Rajada, an area near Chiclayo. The tombs in the area are of adobe construction, of pyramidal shape, and have now shown erosion which could have been exacerbated over time by successive El Niño events. There is very little research on the commoners of Sipán, yet it is well known that the commoners often paid a tax through labor which allowed for the creation of the burial platforms for the Lords of Sipán.^[4] These platforms and other adobe structures are often made with marked adobe bricks which tracked this labor in order to pay off taxes.^[5] Other than providing labor for the Lord there is very little known specifically about Moche commoners from Sipán.

The tombs of Sipán allowed for archaeologists and anthropologists to get a better understanding of the Sacrifice Ceremony of the Sipán rulers that had been illustrated on murals, ceramics, and other decorative goods.^[6] The Sacrifice Ceremonies were often depicted with prisoners among gods or royalty.^[7] The tombs at Sipán showed that rulers actually took part in such Sacrifice Ceremonies when looking at the artifacts uncovered including: adornments and a headdress that matched the illustrations of the ceremony along with large knives and tools that would have been used for bloodletting and decapitation.^[8][9]

In February 1987, a man by the name of Ernil Bernal led a band of huaqueros (tomb looters) who tunneled into one of the pyramids located at Huaca Rajada. Over the next few nights, they took a large number of valuable metal objects, destroying hundreds of ceramics and human remains in the process. Untold numbers of artifacts were lost, sold for profit to private collections on the black market.^[10] Alva arrived with the police a day or more later, after an exceedingly ornate mask had been confiscated from the huaqueros stash house and presented to the researcher.^[11] There are a number of accounts from the events taking place upon the arrival of Alva and the police, however it is clear that they were able to drive the huaqueros away from the site, erect fences around the tombs, and begin excavation.^[12] Thereafter Alva and his team excavated 12 more tombs while villagers and huaqueros threw rocks and taunted them in an attempt to get the researchers out of the site and allow the looting to continue. The villagers were unsuccessful, however, as Alva completed his work which became the foundation of the "Royal Tombs of Sipán" discussed below.^[13][14]

During the excavations in 1987–1990, a spectacular treasure of gold and silver ornamental and ceremonial artifacts was recovered, dating to AD 50–300.^[15] These objects demonstrate the outstanding craftsmanship of the Moche metalsmiths through their use of elaborate and advanced metalworking techniques. Moche smiths made these artifacts out of thin sheets of copper alloys, using electrochemical processes to purify an extremely thin (0.5–2.0 μm) layers of gold or silver coating.^[16]

To make the artifacts, copper ingots were hammered into sheet metal and formed into the desired shape (e.g. a mask). While the exact method for adding the gold film to the outside is not known, one well-accepted theory is that gold was likely dissolved in aqueous solutions of corrosive compounds recovered from the Northern Peruvian deserts and brought to a low boil, after which the copper sheet was dipped in resulting in the reaction:

2Au³⁺ + 3Cu ⇌  2Au⁰ + 3Cu²⁺

thereby dissolving copper and depositing gold on the surface of the metal. The sheet is then heated to between 500 and 800_oC, allowing the gold film to permanently bond to the surface. These gold films were not pure gold, but have been found to be of gold-copper-silver solutions (ex. Cu₂₈Au₂Ag).^[17][18]

Some of the silver artifacts (namely individually made head-shaped beads, about 4.0 cm by 5.1 cm) were formed by alternating between hammering and annealing copper-silver alloy (Cu₁₈Ag₁Au) resulting in copper-oxide forming along the surface which can be removed using an acid (plant juices) or base (stale urine that has turned to ammonia). After many repetitions, the copper will be depleted resulting in the appearance of pure silver (in actuality silver only makes up 18% of the surface).^[19] Other silver artifacts are believed to have been made in roughly the same manner, but contain as much as 90% silver on the surface ^[20]

Examples of metalwork found in Sipán include the above-mentioned head-shaped beads, peanut-shaped beads, coffin straps, fan handles, spearheads, a copper-plated banner, ceremonial knives, golden headdresses, silver and gold nose and ear ornaments, scepters, a gold necklace made of 10 spiderweb beads (spider bodies with human faces sitting on golden wires), a gilded copper animal (possibly fox or dog), among others.^[21] The vast majority of these works were placed in richly decorated tombs, indicating both their high value toward the Sipán leadership and the frequent need for artisans to continue to make new artifacts as old ones were buried.^[22]

• Pampa Grande is located about 10 km to the east from Sipán along the Chancay River valley.
• Chiclayo is located about 29 km to the west of Sipán.
• Lambayeque is located about 40 km to the west-northwest of Sipán.
• Pacatnamu is located about 58 km to the south of Sipán.