Olympus Mons is the largest volcano in the solar system. It rises approximately 21.9 kilometres above the Martian mean surface level and spans roughly 600 kilometres at its base — larger than the state of Arizona. The shield volcano has been volcanically inactive for tens of millions of years but remains intact due to Mars's lack of plate tectonics, which on Earth cause volcanic structures to erode and subduct over geological time. The caldera at the summit is 80 kilometres in diameter and contains a complex of nested pit structures formed by successive collapse events as magma chambers emptied during past eruptions.

The Caldera Rim excursion is a Pathfinder class-exclusive experience available on Inner Planets Survey and Grand Solar Tour voyages with Mars stays. It involves a pressurised shuttle flight from Mars Colony 1 to a base camp at approximately 19 kilometres elevation, a guide-led traverse to the caldera rim at 21.9 kilometres, and a return to base camp for the shuttle flight back. Total excursion duration is approximately 10 hours. The caldera rim presents an unobstructed view into a collapse complex 80 kilometres wide and several kilometres deep; the scale is not intuitively graspable from a single viewpoint, and most passengers describe a period of simply sitting at the rim attempting to understand what they are looking at.

The Olympus Fitness Test is a prerequisite for the Caldera Rim excursion and must be completed at Mars Colony 1 at least 48 hours before the scheduled excursion departure. The test assesses cardiovascular and musculoskeletal capacity for sustained exertion in the Mars EVA suit at Martian atmospheric pressure and gravity conditions. It takes approximately two hours and is conducted by Pelorus Voyages medical staff at the MC-1 expedition wing. The test is pass/fail; passengers who do not pass are not eligible for the Caldera Rim excursion on that voyage, and the excursion fee is refunded. A passed test result is valid only for the current voyage.

The standard medical clearance required for the voyage is not a substitute for the Olympus Fitness Test. Passengers with a valid medical clearance who have not completed the Olympus Fitness Test will be turned away at the Caldera Rim excursion departure gate. Pathfinder passengers should book the fitness test for the first morning of the Mars stay to allow maximum time before the excursion window.
