Since you're in the UK and the property is in Barcelona, I'm guessing this British term will do.

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Note added at 1 hr (2020-10-26 15:27:23 GMT)
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"A block of flats or apartments designed for the appearance of grandeur." - Wikipedia

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Note added at 1 hr (2020-10-26 15:28:22 GMT)
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Or "elegant property" if you want international English.

Suitable jargon? Loft in a high-quality property

Addspace Loft & Extension specialists based and working in ...www.addspaceprojects.co.uk
... high quality property extensions, loft conversions, refurbishments and general building work. We also provide complete property services including bathrooms, ...

Property Refurbishment West London - MAF Contracts Ltdmafcontracts.co.uk › home › property-refurbishment-w...
MAF Contracts "A highly reputable building company with a track record of providing high-quality property refurbishments and maintenance." CONTACT US "A ...

Services of Essex Builders - Loft Conversions, House ...www.edenwood-building-services.co.uk › services
The various building services that we offer in Essex and London, Loft ... We commit to building you a high quality property and within your budgets and ...

I believe "noble" refers to the quality of construction/design etc.

See the fifth definition here:

https://www.wordreference.com/definicion/noble

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Note added at 1 hora (2020-10-26 15:49:19 GMT)
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For example:

https://www.luxhabitat.es/en/barcelona/gotic/piso-con-caract...

Possible description term for an exclusive city centre block.

A manor house was historically the main residence of the lord of the manor.

https://en.wikipedia.org/wiki/Manor_house

Manor Farm is the name traditionally given to the farm of a manor house in England. Its produce was used to supply the manor.

https://en.wikipedia.org/wiki/Manor_Farm

Yes, a "manor" usually denotes a country house surrounded by acres of land, and its origins date back to the days of feudal lords. A "mansion" is nowadays simply another word for a very large house and tends to be used a lot by estate agents in order to inflate the selling price of otherwise relatively ordinary houses

https://www.houzz.co.uk/photos/historia-de-una-finca-noble-t...

Finca noble

https://www.houzz.co.uk/photos/historia-de-una-finca-noble-t...

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Note added at 3 hrs (2020-10-26 17:35:07 GMT)
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Thank you for the explanation. I originally thought of a manor house as in "finca" of a feudal lord. However, looking at the RAE online:

Finca: 1. f. Propiedad inmueble, rústica o urbana.

Finca would then only be 'real estate'

What about Exclusive real estate?

I looked at the building in the link and it doesn't look at all "noble" to me. However, the interiors are probably really nice and in Spain that's what posh flats can look like on the outside.

(I find it rather amusing some people are going for the mansion/manor/country estate vibe... probably misled by the "noble" part).

https://www.airbnb.co.in/rooms/1563723?source_impression_id=...

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Note added at 4 hrs (2020-10-26 18:39:42 GMT)
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NB: OK, "swanky" Is rather informal, but it's widely used on sites like Air B&B and trip advisor.
If you want to go the stiff and formal route, then something along the lines of James's "prime residential" suggestion should work.

I would suggest