You need to be far some specific about what you are looking for. Are you just looking for somewhere with a kiddie pool? Or somewhere to do sightseeing + things a toddler might want to do?

London has loads of things for toddlers to do. The Churchill would be a good choice.

The Hyatt Centric and Thompson in Madrid have treated my 3 year-old amazingly well, but I wouldn't say that Madrid is the best for entertaining her (especially if you aren't a Spanish speaker)