Apartment Therapy featured this simple, secret wall compartment hidden behind a pivoting panel. This panel is decorated with a #5 and conceals electronics, but it can be designed to fit whatever environment.
This custom installation, documented on Imgur, shows a hot tub mounted in the floor near a fireplace. It can be completely hidden under a “walk on” cover and an area rug.
This custom mahogany dresser featured on LumberJocks includes a large fold down compartment in the rear. It’s not easy access, but it would be an inconspicuous hiding spot for long term storage of valuables.