Club 26 was the largest illegal casino in the Netherlands, way before the official Holland Casinos opened.
Club 26 and the Cabala were located in Amsterdam which also included Casa Rosso, a sexclub. Hence the pink elephant logo.
The whole complex was damaged badly by an angry ex employee who set fire to the place.

Holland Casino is the only official casino operator in the Netherlands.
There are numerous arcades which can call themselves 'Casino' since that word is not protected by Dutch law.
The biggest difference with the Holland Casinos is that the arcades don't offer table games, only in electronic form.