Battle of Helsingborg (1362)

Øresund or Öresund (UK: , US: ; Danish: Øresund [ˈøːɐˌsɔnˀ]; Swedish: Öresund [œːrɛˈsɵnːd]), commonly known in English as the Sound, is a strait which forms the Danish–Swedish border, separating Zealand (Denmark) from Scania (Sweden). The strait has a length of 118 kilometres (73 mi); its width varies from 4 kilometres (2.5 mi) to 28 kilometres (17 mi). The narrowest point is between Helsingør in Denmark and Helsingborg in Sweden. Øresund, along with the Great Belt, the Little Belt and the Kiel Canal, is one of four waterways that connect the Baltic Sea to the Atlantic Ocean via Kattegat, Skagerrak, and the North Sea; this makes it one of the busiest waterways in the world. The Øresund Bridge, between the Danish capital Copenhagen and the Swedish city of Malmö, inaugurated on 1 July 2000, connects a bi-national metropolitan area with close to 4 million inhabitants. The HH Ferry route, between Helsingør, Denmark and Helsingborg, Sweden, in the northern part of Øresund, is one of the world's busiest international ferry routes, with more than 70 departures from each harbour per day. Øresund is a geologically young strait that formed 8,500–8,000 years ago as a result of rising sea levels. Previously, the Ancylus Lake, a fresh-water body occupying the Baltic basin, had been connected to the sea solely via the Great Belt. The incursion of salt water via Øresund marked the beginning of the modern Baltic Sea as a salt-water body.

The Battle of the Sound was a naval engagement which took place on 8 November 1658 (29 October O.S.) during the Second Northern War, near the Sound or Øresund, just north of the Danish capital, Copenhagen. Sweden had invaded Denmark and an army under Charles X of Sweden had Copenhagen itself under siege. The Dutch fleet was sent to prevent Sweden from gaining control of both sides of the Sound and thereby controlling access to the Baltic Sea as well as of its trade. The Dutch, under the command of Lieutenant-Admiral Jacob van Wassenaer Obdam with Egbert Bartholomeusz Kortenaer as his flag captain, who had sailed to the Baltic in support of Denmark, had 41 ships with 1,413 guns while the Swedes, under Lord High Admiral Carl Gustaf Wrangel, had 45 ships with 1,838 guns. The Dutch were grouped into three squadrons, while the Swedes separated their ships into four. The seven Danish ships with about 280 guns were unable to assist their Dutch allies because of adverse northern winds and could only watch. Obdam, who initially received written instructions from the Grand Pensionary, Johan de Witt that were very complicated and confusing to Obdam. He requested the orders to be given to him again "in three words", with de Witt replying with a single sentence: "Save Copenhagen and punch in the face anyone who tries to prevent it". The "anyone" was a reference to the English, whose powerful fleet had recently defeated the Dutch in the First Anglo-Dutch War, leading to the Dutch suspecting an English fleet present might come to the aid of the Swedish, although the English simply observed the fighting from a distance, being allied to neither side. The Swedes attacked aggressively, but failed to gain the upper hand, primarily because the approaching Dutch had the weather gage. The Dutch forced the Swedish fleet to end the blockade of the Danish capital, enabling its resupply by Dutch armed transport ships, which eventually forced Charles to abandon the siege entirely. The Swedes lost five ships in the action compared to one Dutch ship, however, the remaining allied ships were more damaged. Also, considering the slightly fewer losses of men in the Swedish navy, 1,200 compared to 1,400 (439 killed, 269 captured and slightly more than 650 wounded allies), the battle is considered a tactical draw. Strategically, however, it was a major allied victory.

The Sound Dues (or Sound Tolls; Danish: Øresundstolden) were a toll on the use of the Øresund, or "Sound" strait separating the modern day borders of Denmark and Sweden. The tolls constituted up to two thirds of Denmark's state income in the 16th and 17th centuries. The dues were introduced by King Eric of Pomerania in 1429 and remained in effect until the Copenhagen Convention of 1857 (with the sole exception of Swedish ships between 1660 and 1712). Tolls in the Great Belt had been collected by the Danish Crown at least a century prior to the establishment of the dues by Eric of Pomerania.

Flakfortet, meaning sand-shoal fortress, is a sea fort located on the artificially built island of Saltholmrev, in the Øresund between Copenhagen and Saltholm. The island and fort are simply known as Flakfortet; the name of the island; Saltholmrev, meaning the reef near Saltholm, is seldom used. Flakfortet was the last of three artificial islands that the Danes created to defend the entrance to Copenhagen's harbor. (The other two are Trekroner Fort (the oldest) and Middelgrundsfortet.) Flakfortet's guns covered the Hollænderdybet channel between Middelgrundsfortet and Saltholm, and the Flinterenden channel between Sweden and Saltholm. Eventually Flakfortet became more of a site for anti-aircraft weapons than for coastal artillery. Its military functions ended in 1968. Flakfortet is currently used for recreational purposes such as concerts, and the site has a restaurant and yacht moorings. During the summer, a ferry company, Spar Shipping, has five scheduled trips per day to the island, with the trip from Nyhavn taking about 40 minutes each way. There is an overnight hostel on the island too.

Indfødsretten (Danish, lit. Citizenship) was a 64-gun ship of the line in the Royal Dano-Norwegian Navy commissioned in 1787. She was one of a class of five ships designed and constructed by naval architect Henrik Gerner.

Middelgrundsfortet or Fort Middelgrund, known as Ungdomsøen (The Youth Island) since 2015, is a sea fort located on an artificial island in the Øresund between Copenhagen and Malmö. The fortress is constructed at a point where the seabed is 7 meters below the water surface, and at the northern meeting point of the straits Kongedybet and Hollænderdybet.

Ungdomsøen (The Youth Island) is a youth camp located on the artificial island of Middelgrundsfortet in the Øresund sound between Copenhagen and Malmö.

Middelgrunden is a shoal in the Øresund, the strait that separates Denmark from Sweden. It is the site of the Middelgrunden wind farm and the Middelgrundsfortet.

The Middelgrunden wind farm stands on the shoal Middelgrunden, between shipping lanes in the Øresund, 3.5 km outside Copenhagen, Denmark. When it was built in 2000, it was the world's largest offshore farm, with 20 turbines (2 MW Bonus each) and a capacity of 40 MW. The farm delivers about 4% of the power for Copenhagen.In 1996, the project was initiated by the Copenhagen Environment and Energy Office (CEEO) after Middelgrunden had been listed as a potential site in the Danish Action Plan for Offshore Wind. Together with the CEEO a group of local people formed the Middelgrunden Wind Turbine Cooperative and established a cooperation with Copenhagen Energy, the local electric utility. The proposed location was initially opposed by the Danish Society for Nature Conservation, but this decision was later changed. Concrete gravity base foundations were chosen as the cheapest option.This project is an example for community wind energy. It is 50% owned by the 10,000 investors in the Middelgrunden Wind Turbine Cooperative, and 50% by the municipal utility company. It is clearly visible from the capital of Denmark.

Saltholm (Danish pronunciation: [sæltˈhʌlˀm]; Salt Islet) is a Danish island in the Øresund, the strait that separates Denmark and Sweden. It is located to the east of the Danish island of Amager in Tårnby municipality and lies just to the west of the sea border between Denmark and Sweden. It is 7 km long and 3 km wide, covering an area of 16 km2, making it Denmark's 21st largest island. Saltholm is very flat; its highest point stands only 2 m (6 ft) above sea level, rendering it vulnerable to flooding if persistent east winds cause a tidal surge in the Baltic Sea. It is a relatively new landmass in geological terms, having risen from the sea about 4,000 years ago due to post-glacial rebound, and is surrounded by a large area of shallow water (of 2 m depth or less) that covers an area of 28 km2 (11 sq mi). A series of islets, inlets and rock deposits from the last ice age appear at the south end of the island. Its neighboring island to the south is the artificial island Peberholm (Pepper Islet), which is a part of the Øresund Bridge and was named to complement Saltholm.

Prøvestenen, also known as Benzinøen, is an artificial island off the northeast coast of Amager in Copenhagen, Denmark. It is located between the Amager Hill combined incineration plant and ski slope to the north and Amager Strandpark to the south. It was created as a marine fortress to guard the entrance to Copenhagen Harbour in the second half of the 18th century and served military purposes until 1922. It now houses the city's petroleum harbor. Prøvestensbroen at the end of Prags Boulevard links it with the rest of Amager.

Öresundsvarvet was a Swedish shipyard in Landskrona that was established in 1915 and largely phased out between 1980 and 1982.