The ancient fortress of Nienhans was once elevated at the confluence of the Ohta River and the Neva, almost in the very center of modern Saint Petersburg. For the Swedes, it was an important stronghold on Russian lands and, due to its location, became one of the thriving trade and economic centers.

Over time, the city engulfed the fortress, but its main victory came nearly 150 years after its disappearance.

In the early 17th century, at the mouth of the Ohta into the Neva, the Swedish town of Nien appeared, protected by the fortress of Nyenskans. During the Time of Troubles, the Swedes sought to strengthen their influence on Russian lands, especially at the strategic mouth of the Neva, which became one of the most important tasks for Charles IX. Due to frequent floods, the marshy lands by the Neva were unsuitable for construction, so after hydrological studies, they chose Ohta Cape, which remained safe from floods.

The first settlements here existed as early as the early Middle Ages. In 1300, the Swedes attempted to establish themselves in this area, but unsuccessfully. In 1611, Charles IX again chose Ohta Cape for the construction of a fortress. After the Swedish War of 1610-1617, the Izhora lands remained with the Swedes.

The first fortress was square, but later it was rebuilt into a hexagon for maximum use of its advantageous position. Inside was a castle surrounded by an earthen rampart and powerful artillery, while to the south and east, the fortress was protected by three bastions.

In 1632, under the protection of the citadel, the town of Nien began to develop. Safety and lively trade made it prosperous. The town had two Lutheran churches, a market, a school, and a port. Relations between religious groups remained tense, especially between the Swedes and Germans, leading to the construction of a separate church for the German community. Orthodox Christians attended the church in the neighboring village of Spasskoye, where the Smolny Monastery now stands.

In Nien lived Swedes, Germans, Russians, and Finns. The town, with 400 households, occupied both banks of the Neva and was connected to the fortress by a bridge. It developed rapidly and soon surpassed Noteborg in wealth. The population exceeded 2000 people. The geographical location contributed to its growth, and new houses were built outside the fortifications, on islands and along rivers in the delta of the Neva.

However, in 1680, oppression of the Russian-speaking population began. The church in Spasskoye was closed, Russians were forbidden to settle in the town and speak their native language. The restrictions also affected the indigenous Izhorians and Karelians.

The Swedes did not pride themselves on the fortress for long. After the war with Russia from 1656 to 1661, it became clear that the fortification needed modernization. The Russians took Nienhans and carried away cannons and armaments. Fearing a new war, Sweden began the reconstruction of the fortress in 1659. The new fortification was significantly larger, with a rampart 19 m thick and 13 m high, as well as a moat with a palisade. The width of the fortification was 28 m.

The area of the fortress increased, but there was not enough land, so engineers added part of the shore, making Nienhans one of the first "reclaimed" projects. It was planned to move the town behind the fortress walls, but due to a lack of funds, they limited themselves to additional fortifications. The garrison could accommodate up to 700 people and 80 cannons.

With the start of the Great Northern War and the capture of Noteborg, the population of Nien increased due to refugees. The Swedish command ordered the town to be burned to complicate the siege, but this did not affect the outcome. On May 1, 1703, troops under the command of Boris Sheremetev captured the fortress. It was renamed Shlotburg and partially used for storage. Russia gained access to the Baltic Sea, while Sweden lost a strategic stronghold.

The fortress existed until 1744, after which greenhouses and a nursery were established on its site. After 1790, the area passed to the naval department, where shipyards were built. In the 19th century, the territory was absorbed by Saint Petersburg. The last mention of Nienhans dates back to the mid-19th century.

In 1992, excavations began at Ohta Cape, and in 2001, the area was declared an archaeological monument. In 2006, the land was purchased for the construction of an office building, which led to legal disputes. Archaeologists refused to permit construction, and the public demanded that the development be halted. Ultimately, the office project was abandoned, and work on studying the finds continued. Thus, Nienhans won its last battle nearly 200 years later.

At the site of the fortress, archaeologists found numerous household items, coins, and artifacts made of birch bark, amber, and metal. The excavation area covered about 40,000 m², making it the largest in Russia. Remains of the fortress of Landskrona, destroyed by the troops of Andrei Gorodetsky, son of Alexander Nevsky, were also found.

At English Embankment No. 6, there was for a time a museum dedicated to the history of Nienhans, where finds telling about the life of the fortress and the town were exhibited. A memorial sign in the form of a miniature pentagonal citadel has been erected at the site of the former Nienhans. Today, the remains of the fortifications are considered cultural heritage sites.