I do see what you mean, museums being 'on-topic' and B&Bs being 'off-topic'. However, it still doesn't seem like a great idea to have museums in there with the sites. Sites being sites, and museums hosting finds from the sites. TMA is quite amenable to having the locations of lost sites included (preferably with "(Destroyed)" or ("Site of") included in the site's title). Maybe there's a middle ground here that could be adequately explored. But, having 'Museum' as a site type would be open to misuse and abuse.