If this entrance is near bathrooms, it is very likely sewage & possibly a vent issue as a PP stated, or a floor drain. I manage facilities for a large retail chain & the bathroom floor drain smelling is very common in our stores. There is supposed to be water in the drain that dissipates the sewer gases. For one reason or another, the water will often evaporate &/or dry up, allowing the sewer gases to rise up. All that is required to fix it, is to pour a couple cups of regular water down the drain. The issue could always reoccur, but then it's just the same easy fix. So, whoever goes there next, maybe you should try pouring water down the floor drain & see if we can help Disney fix this.