According to legend, the Korela fortress was founded by Prince Rurik in 879.

At the same time, the first written mention of the Korela settlement dates back to 1295. The fortress was established at the turn of the 13th and 14th centuries by the Novgorodians on an island in the Uzerva (Vuoksa) River to protect the northwestern borders of the republic from the Swedes.

The Korela tribe is mentioned in Novgorod birch bark manuscripts from 1066, and in chronicles from 1143. It is known that from 1250, local tribes (Korela, Vod) began paying tribute to Novgorod. In 1227, during the reign of Prince Yaroslav Vsevolodovich, the Korelas adopted Orthodoxy.

There was no permanent Russian military garrison or Russian administration in Korela yet. Like all lands of the tribes subordinate to Novgorod, Korela was governed by local nobility who supported Novgorod’s authority.

Until the 16th century, the Vuoksa River flowed in two channels. Part of its water flowed east into Lake Ladoga. The other part flowed west and emptied into the Gulf of Finland near the present-day location of Vyborg. The route "from the Varangians to the Greeks" went along the Neva, while the Vuoksa was a parallel, backup route. The continuous struggle with the Swedes was over control of this second route. The Swedes established Vyborg and then moved east.

In 1293, Torkel Knutsson captured the fortress, but in 1295 the Novgorodians retook it. An unknown author of the "Eric’s Chronicle," thirty years after these events, wrote about it as follows (the Swedes called only themselves Christians):

Kexholm was then taken

The Christians did not burn the town.

The pagan army was defeated,

many were killed by arrows.

Those who survived were taken captive,

brought to Vyborg, inside the stone walls.

The Christian warriors stayed there,

and some were preparing to go home

Each took the goods they could.

Their leader did not manage to escape.

The Russians decided to take revenge —

they would not forget or forgive their shame.

The fortress lacked food,

the Russian army suddenly attacked.

They attacked day and night,

perhaps only the fortress could help the Christians.

They lived there six days without food.

A miracle apparently saved them from disaster!

However, they went outside to fight,

they could not hold out any longer.

They were too weak,

many died of hunger.

Many Russians died in that battle,

the cries of the wounded were heard far away.

The Swedes pressed with their strength,

the Russians fled in fear.

The Christians did not save their lives.

Yes, for the suffering they caused,

the Russians will surely go to hell.

The Swedes are awaited in vain at home.

Sigurd Loke was killed there.

God will shelter his soul in paradise

and the souls of those who in troubled times

gave their lives for the holy faith.

So the Russians took that fortress.

They themselves fortified it from then on,

placing wise men in the fortress,

so that no Christians would be near it.

Sigurd Loke was the fortress commandant and died during the Novgorodians’ attack on it. This is succinctly recorded in the Novgorod First Chronicle: "The Swedes, with their commander Sig, built a town in Korela; the Novgorodians came and destroyed the town, and killed Sig, not sparing a man":

The old fortification on the island was dismantled, and a large earthen rampart surrounding the island was built here, as well as a powerful log fortress wall.

The wooden walls built in 1310 were destroyed fifty years later in a fire so severe that "the townspeople only remained with their souls."

According to the Treaty of Nöteborg of 1323, Novgorod had to recognize the transfer of its former possessions—the western half of the Karelian Isthmus—to Swedish rule. The border, running from the mouth of the Sestra River from south to north, divided the Karelian Isthmus into two parts—Russian and Swedish. Thus, Korela became a border town. The border lasted almost three hundred years, although raids back and forth occurred constantly on both sides.

In the 14th century, Korela covered an area of 6,000 square meters, consisted of about a hundred log houses, and had a population of 300 people. The town’s inhabitants engaged in agriculture and fishing and practiced Christianity. According to the Avraamka Chronicle, in 1364, during the fortress’s restoration after a fire, the first stone structure appeared: "In the Korela town, the posadnik Yakov built a stone furnace." For a long time, it was believed that this round tower in plan survived to the present day. However, excavations showed that the only existing tower on the kremlin territory is a Swedish-era structure, which can be dated to the second half of the 16th century. From the 1330s, Korela was governed by Lithuanian princes Narimantas and Patrikas.

In 1573–1578, a new fortress was built on two islands.

During the Livonian War, in 1580, the dilapidated kremlin was captured by the Swedes, who rebuilt it. By the Treaty of Teusina in 1595, the fortress returned to Russia. Tsar Vasily Shuisky, according to a treaty signed with the Swedes in February 1609 in Vyborg, promised Korela with its district to the Swedish commander Delagardi in exchange for help in suppressing the Time of Troubles (providing Swedish troops and mercenaries during Delagardi’s campaign). Nevertheless, the local population refused to recognize the terms of the 1609 treaty. After Vasily Shuisky was overthrown in mid-summer 1610, Jakob Delagardi decided to seize Korela by force. In the absence of regular troops, a militia was assembled from the local population to defend Korela. Two thousand militiamen and 500 streltsy under the command of voivodes I. M. Pushkin, A. Bezobrazov, V. Abramov, and Bishop Sylvester stood for the fortress’s defense. The defense was led by Ivan Mikhailovich Pushkin the Younger. In 1610, he, along with A. Bezobrazov, arrived in Korela to negotiate with Delagardi. From September 1610 to March 1611, the fortress was besieged by Delagardi’s troops, ending with the defenders’ complete exhaustion and the surrender of Korela. About 100 defenders survived the siege and retreated to Russian lands.

As a result, for a century—from 1611 to 1710—the fortress remained Swedish and was called Kexholm. The Swedes rebuilt not only the Old Fortress, erecting the Round Tower, arsenal, powder magazine, and cladding the earthen ramparts with granite, but also built a New Fortress on the neighboring island according to the bastion system. Judging by old engravings, the New Fortress was 3–4 times larger than the old one. It had five bastions: Leht, Piper, Serk, Fam, and Schwarz. The western and eastern curtains were protected by ravelins. The fortresses were connected by an underwater passage beneath the swift waters of the Vuoksa.

Thus, the Korela fortress was located on two islands at the mouth of the Vuoksa River. The surviving ensemble of the Old Fortress is situated on the site of the kremlin, which was founded at the turn of the 13th and 14th centuries on the small island. Over time, the town expanded onto the neighboring Spassky Island, which was much larger. The Old and New Fortresses were connected by a bridge. Spassky Island was separated from the northern bank by a branch of the Vuoksa River—the Fedorovskaya River—over which a bridge was also built. After 1857, when the Vuoksa changed its course, the water level in the river dropped, and the channels separating the islands dried up. The New Fortress ended up on the northern bank of the river, and the Old Fortress—in the western part of the vast Kukushkin Island.

On plans and engravings from the 17th–18th centuries, the Kexholm fortress (also called the Kremlin Island or Old Fortress) was depicted as having a single tower. The surviving low (8 meters) round gate tower (Lars Torstensson’s Tower or Pugachev Tower) was located opposite the bridge connecting the Old Fortress with Spassky Island. The tower is two-tiered, with later blocked gun embrasures. The tower walls are very thick (4 meters in the lower tier), indicating that by the time of construction, firearm fortifications were already well developed. Such towers were built in the Swedish kingdom by Saxon masters from the early 1540s.

The fortress’s defensive structures, besides the round gate tower, included two bastions named Clock Bastion (Chasovoy) and Bath Bastion (Bastu), connected with the Round Tower and with each other by low curtains. In the fortress yard are the Old Arsenal, Powder Magazine with Cavalier Bastion, and New Arsenal. A large stone powder magazine, partially dug into the ground, adjoins the Old Arsenal on the northeast side. An arched entrance leads down from the fortress yard through a wall up to 5 meters thick. On the vaults of the magazine, on a powerful earthen rampart, a bastion was built, called the Trumpet Bastion in the 17th century and the Cavalier Bastion in the 18th century. Besides the main gates, the fortress had the Clock Gate under the Clock Bastion and the Water (or Mill) Gate located in the southeastern curtain.

In September 1710, the fortress was captured by Russian troops led by commander Roman Bruce. In honor of the victory, the emperor ordered the Swedish armor to be unshackled and all the gates of the New Fortress to be decorated with it. Only one gate has survived to this day. It can be seen today in the fortress museum.

Peter the Great visited the fortress after its capture. In 1741–1743, the fortress’s defense was strengthened by the Pernov Redoubts, built on the Perna River 5 kilometers north of Kexholm. From the second half of the 18th century, the fortress was used as a prison. After Finland’s annexation to Russia in 1810, the Kexholm fortress was abolished, but the prison remained.

In the 18th–19th centuries, it served as a prison for political prisoners (in particular, the family of Yemelyan Pugachev https://reveal.world/story/uzilishche-sem-i-pugacheva and the Decembrists) and is associated with the legend of the Russian Iron Mask and the mysterious nameless prisoner https://reveal.world/story/russkaya-zheleznaya-maska-2.

Sources:

https://ru.wikipedia.org/wiki/Корела_(крепость)

https://ch.itmo.ru/nwfortress/kreposti/krepost-korela

https://tamtravel.ru/leningradskaya-oblast/stati-o-turisme-v-leningradskoj-oblasti/vse-legendy-i-byli-staroj-kreposti-korela/#tit1

https://amsmolich.livejournal.com/169876.html