What is an SPA?
I assume, because you typed it in capitals, that this is an acronym, not the normal word spa
It would help if you could tell us where you found this and quote the full sentence, at least.
From Wikipedia A destination spa is a short term residential/lodging facility with the primary purpose of providing individual services for spa-goers to develop healthy habits. Historically many such spas were developed at the location of natural hot springs or sources of mineral waters. Typically over a seven-day stay, such facilities provide a comprehensive program that includes spa services, physical fitness activities, wellness education, healthy cuisine and special interest programming.
A large destination spa is a big one of those
I've never heard the term before.