Can you explain why Marco Polo took so long to travel to China and back?

The geographical and climatic difficulties encountered during the journey.

Marco Polo had to traverse some seriously complicated territories, moving from burning deserts to the glacial mountains of Central Asia. The crossing of the Gobi Desert, in particular, was harsh: intense heat during the day, freezing cold at night, and scarce water sources. The rugged terrain of the Silk Road didn't help matters. He had to navigate around steep mountains and valleys like the Pamir, nicknamed the "roof of the world," with passes to cross over 4,000 meters in altitude. These extreme terrains could seriously slow down the entire expedition, not to mention the snow or sandstorms that often blocked their way. In short, the journey was far from a walk in the park.

Limited means of transportation and their impact on travel duration

Marco Polo didn't have much choice when it came to transportation. At that time, there were no trains, cars, or airplanes of course—just travel on the back of a camel, horse, or mule, or simply walking for hundreds of kilometers. This imposed a slow pace, forced to follow difficult routes, mountain paths, or the often winding trade roads. Some land paths like the famous Silk Road were frankly dangerous or very poorly maintained. At sea, the boats used were rudimentary, primarily propelled by the wind, often requiring significant detours to take advantage of currents and avoid storms. In short, these not very efficient, even downright basic means of transport extended the journey much longer than a comparable trip today.

The political and sociocultural constraints influencing the journey.

At the time of Marco Polo, crossing Asia inevitably involved some political complications. For example, it was often necessary to negotiate access to certain territories controlled by local leaders who were uncooperative or wary of foreigners. Marco Polo had to adapt to the customs and traditions of each region he traversed, in order not to offend anyone and to avoid being turned away at a border. Additionally, periods troubled by conflicts or tribal wars sometimes forced the traveler to wait patiently for a route to become safe again. Another difficulty was obtaining passes, as each passage through a region often required a specific authorization issued by local authorities. This delicate political context and these ongoing sociocultural constraints largely explain why Marco Polo spent so many years making the round trip to China.

The prolonged and unexpected stops experienced by Marco Polo.

Marco Polo spent quite a bit of time stuck in one place, notably due to illnesses, such as when he had to stop for several months in Afghanistan to regain his strength. He also faced severe bad weather, like storms or snow-blocked passes, forcing him to stay in certain villages longer than expected. And above all, when he was staying in certain cities, like Kashgar or in the courtyard of the great Khan, it was often for entire years — the Khan entrusted him with missions or specific tasks that kept him there much longer than he could have imagined at the start. In short, all these unforeseen events, often related to the ups and downs of health, climate, or diplomatic and commercial necessities, explain why his journey dragged on for so long.