The housing association decided it was time for a new boiler. The old one was 23 years old and served me well, but was not very energy efficient. Here's a picture of the old one.
The new one is much smaller, it's smaller than a wall kitchen cabinet. It doesn't only heat the apartment but also delivers hot water. It's more efficient and it gives more hot water than the old one. I'm happy!
Yes, it's a natural gas unit, we have big resources of natural gas, so almost everyone heats with it. The new one has a dual pipe system, it takes the air in from outside. They had to make a new pipe into the old chimney.
My old one was indeed a Vaillant too. In my previous apartment I had an older one too. It had a button that you could set for keeping a small amount of water hot, instant hot water! I think that one was from 1982.