Borders between countries are often considered merely lines on a map. But humankind has carved their footprint on the planet. Now some of those lines can be seen from space. These images from the NASA Earth Observatory image database show the few instances where an international boundary is visible from the heavens.

All of the images were taken either by astronauts on the International Space Station or by satellites orbiting the Earth.

This image from the Expedition 38 crew on the International Space Station in February 2014, shows North Korea almost indistinguishable from the Yellow Sea and Sea of Japan on either side of the country. Only the capital of Pyongyang in the center is visible at night, a marked contrast to its neighbors, China and South Korea.

This International Space Station photo from October 2014 shows the Rio Grande and a wall separating the United States and Mexico. El Paso, Texas, on the U.S. side lays across the river from Ciudad Juárez, Chihuahua, on the Mexico side. Four international points of entry connecting Ciudad Juárez and El Paso: the Bridge of the Americas, Ysleta International Bridge, Paso del Norte Bridge and Stanton Street Bridge.

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), a high resolution imaging instrument that is flying on the Terra satellite, took this infrared photo on May 19, 2000. The right side of the image shows farmlands of California in the United States. The left side is Mexican arid expanses with a few farms dotting the landscape. The border town of Mexicali-Calexico lies in the middle of the image, with El Centro, California to the right. Imperial Valley of California is a major fruit and vegetable producer for the US, watered by canals fed from the Colorado River.

The farmlands of China, sustained through irrigation that pulls about 65% of the country's fresh water, is a stark contrast to its neighbor, Kazakhstan of the former Soviet Union. 10% of land in China is used for farming compared to 0.03% used by Kazakhstan which relies on only a few industrial sized farms. According to NASA, as of 2006, about 629,000 square kilometers (242,858 square miles) of land in China is irrigated, an area only slightly smaller than Texas.

The Expedition 41 crew aboard the International Space Station in November 2014 first thought they were looking at oil pads on this stretch of border between Iran and Iraq. However this almost 20 kilometer (12 mile) line near the Persian Gulf is visible from space for a more deadly reason. The landscape has been altered by circular gun emplacements, connecting roads, and land fortifications running parallel to the boundary. The area was highly contested by the neighboring countries in the 1980s. That conflict has left its mark on the planet.

Another ASTER satellite image, taken July 2, 2008, shows the differences in deforestation between Brazil and Bolivia. Brazil, on the bottom left side, opened their Acre Province in the rainforest to farming and settlement. Bolivia, on the other hand, preserved its native rainforest in the Pando Department, leaving the area in the upper right untouched by development.

Different choices for agriculture industries, not military fortifications, make the countries' border between Israel and Egypt just barely visible from space. This November 2011 image from the Expedition 29 crew aboard the International Space Station shows a visible line between Egypt and Israel. A road separates the two countries and Israel's commercial agriculture results in angular fields while the lighter color of the Egyptian soil is a result of trampling by livestock disrupting the dark soil crusts seen in Israel.

This 2012 picture, taken by astronaut Chris Hadfield and documented by André Kuipers from the International Space Station,.shows some of the remaining differences between the former east and west Berlin. The lights in the eastern part appear yellow, while the lights in the western part are whiter. Why? The western region has more modern, environmentally friendly streetlights.

This 2002 satellite image shows the effects of deforestation in Haiti versus the greener land of the Dominican Republic on the right.

Known as the Radcliffe Line, 2,000 kilometers (1,243 miles) of the India-Pakistan border is floodlit with thousands of troops permanently posted along it.The border is one of the most heavily militarized on Earth with a fence running the entire distance to discourage smuggling and arms trafficking. An expedition 45 crew member aboard the International Space Station took this nighttime panorama in September 2015 while looking across Pakistan's Indus River valley.