The Green Solution is one of the three largest dispensary chains in Colorado, and the 4400 Grape Street location in north Denver really stands out. The dispensary is attached to one of the company's cultivations and has been a mainstay off I-70 since recreational cannabis sales began in 2014. Starting in 2018, customers will get a 360-degree look inside that cultivation, thanks to a new glass tunnel that expands into part of the grow.