The sheer size is almost unimaginable from the perspective of an individual walking around, if the 4 million sq m listed in the article is accurate. For comparison, that means Yiwu is roughly 400x larger than an average Walmart -- and certainly must be much more densely stocked.

I recently visited Seoul's Dongdaemun shopping area and the scale was shocking. It includes dozens of massive, multi-story buildings that span roughly 10 city blocks. When it was built in 1970, it was the largest such market space in Asia. (They claim it is still the largest, but perhaps the distinction is because Yiwu is considered a city.)

If the average city block is ~10k sq m, then 10 blocks with an average of 4 stories per building yields 400k square meters of space.. which is a mere 10% of Yiwu's claimed size -- wow! You could spend weeks walking around Dongdaemun without seeing everything, but the experience was similar to what the article describes Yiwu as -- booth after booth of the same types of mostly wholesale merchandise.