When the first ever Church of Cannabis opens next week, it's gonna be one helluva trip, and that's based purely on the decor.

We got this peek inside the joint, and sure seems like they catering to a high congregation. It will be the first large gathering place in Denver where potheads can smoke and achieve spiritual goals ... without getting arrested.

Its exterior walls were painted by contemporary artist Kenny Scharf. Incredibly, it only took him a day and a half to finish. Spanish artist Okuda San Miguel did the trippy interior.

The ICoC is still raising funds ... they need a new boiler and want to install ramps and an elevator.