Large tasteless house from 1900 redeveloped as "old" inn (9)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

Last (and only previous) time we had this in a daily (a year ago) I suggested Mar-a-Lago might qualify as an example, but apparently McMansions tend to be smaller and in taste-free estate developments. Whatever, it’s clever wordplay: 1900 delivers MCM and the rest is an anagram (redeveloped) of AS OLD INN