At one point directory depth was recommended as a way to advantage keywords, however, today that advice does not hold true. It is believed that the further down in depth you go, the less important the page is. Search engines work on this principle. Having said that, I would recommend some other options with some assumptions.
The assuptions are: I assume that you will have a page that lists/links the various reviews, and that each review has a page.
There is some exception to the depth theory (stated above) that allows one level from the root directory. Going two levels from the root risks losing importance regardless of how it is linked. At one point depth was only measured in links from the root, but now it seems that link and directory depth can count against you as search engines now use these metrics as indicators. Depth is recommended in that a flat site does not take advantage of organization. You see, search engines like balance. Not a flat site, and not too deep. They measure the norm, and anything within the norm is okay. Anything outside, begins to become suspect. It's a metrics game. If the world suddenly shifts to using two levels deep, then my advice would change again.
Please remember that while SEO has taken advantage of a method, there has always been a push back against gaming the system. This often effects the innocent too. That is where we are with depth.
I am not saying you cannot go two levels deep, I am simply not recommending it as an SEO tactic anymore.
If you do not want to expose your web pages, then I suggest: