The iliac veins are large blood vessels located in the pelvis that play a crucial role in returning deoxygenated blood from the lower limbs and pelvic region back to the heart. They are formed by the merging of the femoral veins and the internal iliac veins, and they eventually drain into the inferior vena cava, which carries blood to the heart. There are two main iliac veins on each side of the body: the external iliac vein and the internal iliac vein. The external iliac vein drains blood from the lower extremities, while the internal iliac vein collects blood from the pelvic organs. Proper functioning of the iliac veins is essential for maintaining healthy circulation.