The landing zone (or ‘decompression zone’) is that area immediately inside the entrance of the store. Its size may vary from several square meters in department stores, to something much smaller (almost non-existent) for some specialty stores.
Once you have grabbed customers’ attention and they decide to enter the store, they must undergo a physical and psychological transformation. Watch carefully and you will see how they slow down, fold away the umbrella, pat their pockets, settle the child, adapt to the lighting etc.
People need physical room to ‘decompress’ and this area should not be cluttered.
It feels counter-intuitive to leave some of your (potentially) must productive space empty but one should view it as an investment in space required for customers to mentally and psychologically transition from passerby to browser. This transition is necessary in most stores before you can convert browsers into buyers.
If you are going to break the landing zone rule, then break it properly (create something with WOW) in order to ‘punch’ the customer between the eyes, but do it infrequently in order to retain the ‘surprise’ element.