National boundary delimitation in the context of "Indonesia–Singapore border"

A border barrier, border fence or border wall is a separation barrier that runs along or near an international border. Such barriers are typically constructed for border control purposes such as curbing illegal immigration, human trafficking, and smuggling. Some such barriers are constructed for defence or security reasons. In cases of a disputed or unclear border, erecting a barrier can serve as a de facto unilateral consolidation of a territorial claim that can supersede formal delimitation. A border barrier does not usually indicate the location of the actual border, and is usually constructed unilaterally by a country, without the agreement or cooperation of the other country.

Examples of border walls include the ancient Great Wall of China, a series of walls separating China from nomadic empires to the north. The construction of border barriers increased in the early 2000s; half of all the border barriers built since World War II, which ended in 1945, were built after 2000.

The India–Nepal border is an open international boundary running between the countries of India and Nepal. The 1,751 km (1,088.02 mi) long border includes the Himalayan territories as well as Indo-Gangetic Plain of the subcontinent. The current border was delimited after the Sugauli treaty of 1816 between Nepal and the British Raj. Following Indian independence, the prevailing border was recognised as the international border between the Kingdom of Nepal and the Dominion of India.

The Border Agreement between Poland and the USSR of 16 August 1945 established the borders between the Soviet Union (USSR) and the People's Republic of Poland. It was signed by the Provisional Government of National Unity (Tymczasowy Rząd Jedności Narodowej) formed by the Polish communists. According to the treaty, Poland officially accepted the ceding its pre-war Eastern territory to the USSR (Kresy) which was decided earlier in Yalta already. Some of the territory along the Curzon line, established by Stalin during the course of the war, was returned to Poland. The treaty also recognised the division of the former German East Prussia and ultimately approved the finalised delimitation line between the Soviet Union and Poland: from the Baltic Sea, to the border tripoint with Czechoslovakia in the Carpathians. The agreement entered into force on 5 February 1946.

The Alps form a large mountain range dominating Central Europe, including parts of Italy, France, Switzerland, Liechtenstein, Austria, Slovenia, Slovakia, Germany and Hungary.

This article describes the delimitation of the Alps as a whole and of subdivisions of the range, follows the course of the main chain of the Alps and discusses the lakes and glaciers found in the region.

The border between Norway and Russia consists of a 195.7-kilometer (121.6 mi) land border between Sør-Varanger Municipality, Norway, and Pechengsky District, Russia, and a 23.2-kilometer (14.4 mi) marine border in the Varangerfjord. It further consists of a border between the two countries' exclusive economic zones (EEZ) in the Barents Sea and the Arctic Ocean. Between 1944 and 1991 the border was between Norway and the Soviet Union. There is a single border crossing, on E105, located at Storskog in Norway and Borisoglebsky in Russia. The Norwegian side is patrolled by the Garrison of Sør-Varanger and is under the jurisdiction of the Norwegian Border Commissioner, while the Russian side is patrolled by the Border Guard Service of Russia. Two-thirds of the border follows two rivers, the Pasvikelva and Jakobselva.

The border was defined as a march in a treaty in 1326 and separated which parts of the Sami could be taxed by Norway and Russia. The border line was defined by a treaty in 1826 and essentially remains the same border today. In 1920 Petsamo was ceded to Finland and the border became part of the Finland–Norway border. Petsamo was ceded to the Soviet Union in 1944 and the Norway–Soviet Union border was established. During the Cold War, the border was one of two between the North Atlantic Treaty Organization (NATO) and the Soviet Union, the other being the Soviet Union's border with Turkey. From 1991 to 1999 it was the only border between Russia and NATO. It is Norway's youngest unchanged border. Since the 1960s there has been disagreement as to the border between the two countries' EEZs, but this was resolved by a delimitation agreement in 2010.