Customs change over time – my maternal grandmother wanted to be cremated not buried but did not get her wish. In hindsight I sympathize with my maternal grandfather: he had her respectfully viewed and buried and later was similarly treated the same.
I like having marble monuments where I can honor my grandparents and parents. I have sprinkled the ashes of my parents in multiple locations but the only locations that stilled my grieving were the ones with marble monuments, with stones engraved with birth and death dates.
A mausoleum, as long as the chamber was engraved with birth and death dates, would also be ok.
If there were no mortal remains, the marble monument would be a cenotaph – I think that would have been ok as well: we need some kind of physical place to visit and remember and honor.
image credit: hard news