It would have been around mid-19th century to late-19th century when the Festetics family was heavily involved with construction of hotels in or around Heviz (Hungary)... an important spa region in the area due to the natural thermal lake that had attracted visitors for hundreds of years, prior (and today, too), but at one point the Festetics; in the process of building 'Uj-telep' (new colony) let out to lease land and their spa nearer to the turn of the century (19th)... and that's where I crash into a stone wall. Everything gets so close to actually mentioning this casino, but stops dead of doing so.

Any help would be greatly appreciated.

(Not to be confused with a more recent Hotel Thermal/Casino in Heviz -- I think)