Re-experience your youth in an amazingly annoying fashion with a “scaled up furniture” business featuring gigantic chairs and tables!
Background:
Almost everything in the world is designed for people of average adult size.
As a result, most everyday objects (furniture, stairs, door handles, etc.) are a totally inconvenient size for children or the extremely short.
This is somewhat surprising, since everyone spent many years facing these problems as a small child.
But it was so long ago that no one really remembers! (This is also a classic example of the market failing to address the needs of a demographic with zero purchasing power.)
Proposal:
Here, we propose re-furnishing a shopping mall so that every object is sized to give you (as an adult) the approximate impression of scale that a three- or four-year old would have.
In other words, we approximately double the size of everything in the mall in all three dimensions (e.g. a 3-foot high table is now 6 feet high, and doors are 15+ feet tall).
The building would also need to have an exceptionally high ceiling in order to accommodate the larger furniture (see Figure 1).

Fig. 1: All the furniture is scaled up proportionately. This chair is now basically unusable by the average-height mall patron (left).
Additionally, if this “everything is enormous” business were to sell food or beverages, those should also be scaled up (Figure 2).

Fig. 2: In the spirit of scaling up everything, a “regular sized” coffee would be served in an enormous gallon-sized mug (Figure 2). A hamburger scaled up in this way would contain approximately 6,000 calories.
Conclusion:
Since there are so many malls that have gone out of business due to the convenience of Internet shopping [1], there should be plenty of abandoned real-estate that can be repurposed for this plan.
PROS: Provides useful perspective to product designers. Also allows people to re-live their childhood in the most inconvenient way possible, thus saving them from unwarranted nostalgia.
CONS: The potential for breaking bones in this out-of-scale environment is extremely high. Not everything scales up in a strictly linear fashion (e.g. a fall off a 6-foot-high table would be more than twice as injury-causing as a fall off a three-foot-high table).
[1] (Some people dispute this, and suggest that another factor could have caused it, such as haunting by ghosts.)