Deep in the Atlantic Ocean, there is a powerful system of moving water that can feel almost like a river within the sea. This is part of a larger circulation system called the Atlantic Meridional Overturning Circulation (AMOC), and one of its most well-known components is the Gulf Stream. It carries warm surface water from the Gulf of Mexico along the east coast of the United States and then across the Atlantic toward Europe. The Gulf Stream transports nearly 4 billion cubic feet of water per second, a flow greater than all of the world's rivers combined Unlike a river on land, it doesn’t have fixed banks. Instead, it is a broad, fast-moving current within the ocean, driven by wind patterns, temperature differences, and the Earth’s rotation. As it travels, it gradually spreads out and blends with surrounding waters, becoming part of a much larger global ocean circulation system. Even so, its impact is enormous. The Gulf Stream transports a huge amount of heat northwards, helping to influence weather and climate. In particular, it contributes to making Western Europe milder than other regions at similar latitudes. Rather than a single “hidden river,” it is better understood as a powerful, shifting current system, part of the ocean’s global conveyor belt, constantly moving heat and energy around the planet.

Deep in NW China’s Gansu Province, a high-speed railway winds its way through rolling loess hills. Boring tunnels through mountains has never been an easy feat—yet China makes it happen, all for the people waiting beyond the peaks.

Deep in the ocean is where National Geographic Explorer-in-Residence Tara Roberts feels the greatest wonder, unearthing lost stories through her work with @InsideNatGeo and connecting with the past as part of a community.