A Taj-mahal? It's a tomb... A cat surely shouldn't like this; but a dome, I am sure that any living feel him very well inside.
A look; here for human beings: http://www.i-domehouse.com/case.html
And this, in France: http://www.domespace.com/fr/accueil (but very too much expansive).

There are some good cat cabin made yet in the world, it's new, but that arrives little by little.
Example: http://www.katkabin.co.uk/