Hotter than Hades. Like an oven, hotter inside than outside.
Host Rosi was very nice; owner Franziska was not. When we learned there was no AC, we asked about fans. Franziska's response was that we had the "choice" to leave. Given that we had paid over €2.5K in advance, and there was a no refund policy, this felt more like a threat than a "choice."
The flat is bright and would be lovely in other seasons, but Airbnb should not list it in the summer months until there is an adequate cooling solution. The shutters in the living room were old and broken, and the bedrooms in the rear were only protected by indoor blinds: if you lowered them to block the afternoon sun, they would block the breeze needed to ventilate the flat. My daughter and I are used to the heat, having lived in Oklahoma, and to living without AC, as when we lived in Colorado, but we both found the heat and humidity inside this flat unbearable during the day.
The apartment is not "luxuriously equipped," as they claim. The oven/stove is old, missing buttons, and requires manual lighting, which was a bit dangerous. The old shutters were missing slats. The wifi does not "keep you connected," as claimed: the router is very old, and the connection is extremely unstable, even in the living room. In the bedrooms, the speed was usually just .4 to 1.1 mbps.
In short, needs a cooling solution before it should be rented in the summers.