On World Environment Day, the Copernicus Sentinel-2 mission brings us an amazing view from space of Baku, capital of Azerbaijan, hosting this year’s celebration.
Zoom in to explore this image at its full 10 m resolution.
In this false-colour image, Baku is visible in grey on the southern side of the Absheron Peninsula, seen jutting out from Azerbaijan’s coast for 60 km into the Caspian Sea. The Peninsula protects the city from the harsh winds blowing throughout the year, while the Bay of Baku, sheltered to the south by the Baku Archipelago, provides the best harbour in the Caspian Sea.
Baku is 28 m below sea level, which makes it both the lowest-lying capital and the largest city in the world below sea level. With an area of around 2140 sq km and a population of more than two million people, Baku is also the largest city on the Caspian Sea and the biggest in the Caucasus region.
This image, captured in January 2026, was processed including Sentinel-2’s near-infrared channel, which is most commonly used to assess plant density and health, as plants reflect near-infrared and green light, while absorbing red. Since they reflect more near-infrared than green, dense, plant-covered land appears in bright red.
Water bodies, such as lakes and the Caspian Sea appear in dark blue or black depending on their depth. Turbid waters, such as those visible along the coasts, appear in cyan or light blue, most likely due to sediment flowing from rivers into the sea. Inland water bodies can be spotted in various shades of azure owing to their turbidity.
Variously classed as the world’s largest lake or the smallest full-fledged sea, the Caspian Sea is the largest landlocked water body in the world, with a total surface area of 371 000 sq km. Its enclosed nature means it is home to some unique animals and plants, but it is also vulnerable to pollution from agriculture and industry. The Caspian has experienced large variations in its water level in the last few decades, a development at least partly due to human activity.
Celebrated each year on 5 June, the UN’s World Environment Day focuses on awareness of environmental challenges and action to protect our planet. This year’s focus is on climate change and on the urgent signals the Earth is sending. With impacts already being felt across every region, and the risks accelerating, decision‑makers need reliable evidence for effective action.
Earth Action – a core pillar of the FutureEO programme – is one of ESA’s responses to this urgency. It provides a coordinated framework, that translates ESA’s world-leading Earth observation science, data and applications into trusted, decision‑ready information and solutions to help users anticipate change and act to reduce risk and build resilience.