The very foundation of Petersburg is surrounded by mysticism and legends. The most important one, perhaps, tells that the land on which the future capital of the Russian Empire arose was, to use biblical language, "formless and empty." But this is not true.

Today, everyone already knows about the city of Nienshants, but far from everyone understands what kind of city it was. Nienshants — a German-language variant of the Swedish name Nyenskans (Swedish Nyenskans, "Neva Fortification") established in the Russian language — was a fortress that served as the main fortification of the Swedish city of Nien (Swedish Nyen), or Nienshtadt. The city and its defending fortress were located at the mouth of the Okhta River into the Neva on both its banks. Approximately in the same place, three centuries earlier (in 1300), with the participation of Italian specialists, the Swedes built a wooden-earth fortress Landskrona ("Crown of the Earth") with eight towers, which was taken by the Novgorodians led by Prince Andrey Gorodetsky, son of Alexander Nevsky, after a year and a half and almost completely destroyed.

It is unknown how much time passed before the mouth of the Okhta was resettled again, but the 1500 Vodskaya Pyatina Census Book provides the first description of the local settlements (three villages and a small settlement with 18 households). The lands in the lower course of the Okhta long belonged to two noble boyar families of the Novgorod Republic, and after its annexation in 1478 to Moscow, they became part of the centralized Russian state.

It is known that Ivan Vyrodkov, an engineer-fortifier of Ivan the Terrible, together with Petrov, supervised the construction of a port-fortress at the mouth of the Neva River in 1557. A document dated 1599–1601 mentions the presence in the town of Neva Mouth of the Tsar’s guest yard, a ship pier, and an Orthodox church. Furthermore, it states that "volost people" lived in the town. It is known that only in 1615, during the Russian-Swedish war of 1611–1617, 16 ships came here from Swedish-occupied Ivangorod, Ladoga, Novgorod, as well as from Vyborg, Narva, Norrköping, Reval, and Stockholm.

This captured Russian settlement served as the basis for the city that the Swedes built here at the beginning of the 17th century and even gave it its name: since the Swedish word "nyen" means "Neva," it was used in relation to the Russian settlement even before the Prinievye region was seized by Sweden.

In particular, on a schematic map of Karelia and the Prinievye lands from the 1580s, presumably compiled by order of Pontus De la Gardie, the Neva town is marked (and it can be understood that there was already a church in the town then) precisely as Nyen.

The Swedes chose places for building their fortresses in the Neva delta based on the consideration that the left bank of the Okhta bend was the closest place to the sea not flooded even during catastrophic floods occurring on the Neva once every hundred years. The Swedes used hydrological information about the Neva obtained from local residents. Initially, the fortification located on the Okhta cape had a rectangular shape, but later its outlines changed. On the 1643 map of the Neva mouth, it is already depicted as an irregular hexagon.

In 1617, by the Treaty of Stolbovo, the Izhora land was secured to Sweden. In 1632, on the right bank of the Okhta, opposite the fortress, by order of King Gustav II Adolf, the trading city of Nien (Nienshtadt) was founded. Over the next ten years, Queen Christina (1626–1689) granted it full city rights. In 1656, Russian voivode Pyotr Ivanovich Potemkin stormed Nienshants. According to Russian command reports, the population of Nien was almost completely slaughtered from young to old. Only those who managed to flee into the forest survived. However, after the war, both the fortress and the surrounding territories remained with Sweden.

After this storming, around 1677, the city of Nien was surrounded by an outer ring of fortifications — lunettes with batteries and moats — from the Neva bank to the Okhta bank. Initially, the fortress housed 500 people. By the end of the 17th century, the garrison of the fortress numbered more than 700 people and had about 80 cannons at its disposal. In its final form, according to the updated project implemented by engineer Heinrich von Zoylenberg, the Nienshants fortress represented the most modern fortification of its time in the shape of a star with 5 empty bastions: Karl's, Helmfelt's, Guarn (Mill), Gamle (Old), and Dead, as well as 2 gate ravelins.

The Nienshants fortress occupied the so-called Okhta cape, extending from the northeast to the opposite left bank of the Okhta to Nienshtadt, and from the west to the right bank of the Neva. The city of Nienshtadt stood on the right bank of the Okhta, at the confluence of the Chernavka River, originally called "Black Creek," or in Swedish Lilja Svartabecken. At the mouth of this river into the Okhta (which at that time was called Swarte Beck — Black River), on its right bank was the Market Square and the city hall, and further up on the same bank was a Lutheran church and school.

The Nienshants fortress was founded by the Swedish commander Evert Horn in 1611 on lands seized from Russia under the pretext of non-fulfillment of the Vyborg Treaty. Alternative names for the city and fortress are Nieshants, Schlotburg, Kanets (in old spelling: Ніешанцъ, Шлотбургъ, Канецъ).

Pylyaev in the book "Old Petersburg" reports that in Nien "there were many excellent sawmills and good and beautiful ships were built there; besides the Swedish, Finnish, and German parishes, there was also an Orthodox one. From Nienshants, a ferry went to the left bank of the Neva, to the Russian settlement Spasskoye located there."

Festival in Nien. Eduard Yakushin. Source: piter.livejournal.com

Every August, a three-week fair was held in Nien, attracting merchants from all over Europe and nearby lands. Local merchants conducted extensive trade with Europe, and one more small but strong detail: "...the Russian merchant class in Nienshants entered and brought this place such fame that in recent years one local merchant, nicknamed Frisius, could lend considerable sums of money to the Swedish King Charles XII at the beginning of his war with Peter the Great, for which he was later granted nobility, given the new name Frisengheim, and made a judge in Vilmanstrand."

On the lands where Petersburg now spreads, according to old Swedish maps, there were 41 settlements besides Nienshants. Both Swedes and Russians lived here. For example, on the site where the Winter Palace now stands, there was a Finnish village with the beautiful name Osadissa-saari.

Modern researchers believe that at the time of the city's founding, about six to seven thousand people lived on these lands, which was quite a lot for that time. Thus, Petersburg, contrary to legends, was not built on an empty place. 

Sources:

https://ru.wikipedia.org/wiki/Ниеншанц

https://history.wikireading.ru/220555

https://bigenc.ru/domestic_history/text/2266609

Sorokin P. E.: Landskrona, Neva Mouth, Nienshants. St. Petersburg, 2001.