Penthouse sur la Gran Vía avec bassin-jacuzzi chauffé (p2lhomes)
The hot tub. Outdoor pool on the roof terrace with heating: it works as a jacuzzi at 40 °C or as a cold plunge pool in summer. The terrace is booked privately in 3-hour slots.
I haven't yet found guest reviews that mention the jacuzzi or the water temperature.
Guide's tip. Read the listing carefully: direct bookings get priority; via Airbnb, terrace access can cost €30 per person with no guaranteed slot, and there's no refund if it breaks down.