Final answer:
The kidneys are located in a retroperitoneal position relative to the peritoneal cavity, meaning they are behind it and well-protected by surrounding fat and fascia.
Step-by-step explanation:
The kidneys are located in a retroperitoneal position when compared to the peritoneal cavity. This means they lie behind the cavity, between the parietal peritoneum and the posterior abdominal wall. Covered by fat and fascia, the kidneys are well-protected and slightly differently positioned, with the right kidney being somewhat lower due to the liver's placement. Each kidney is surrounded by a fibrous capsule and a fat layer that cushions them, and the renal fascia helps anchor them firmly in place.