Very beautiful place, like on the photos. However it feels like attention was put more on it being beautiful for photos than on functionality. There's no bed (only a non-convertible sofa, that's not very comfortable for 1, and can't fit 2). And the shower and toilets are extremely small and difficult to access. It's difficult to sit on and stand from the toilets as the knees bump into the sink. And it's very difficult to get into (and even more out) of the shower, even for very thin people. So people above standard sizes may not be able to enter without breaking the door.
Though annoying, we could still use the shower and toilets, and we liked the convenience of the washing machine, fridge, kitchen and smart TV, so we still rate it high!
Also, we didn't know beforehand, but Belleville is among the least safe neighborhoods of Paris. We felt unsafe at night.
At last, the building is very old (though the flat is fully renovated), and the elevator is extremely small and can only accommodate 1 person + 1 luggage at a time. So we had to do 2 elevator trips to go in and out with our luggage.