Just spend half of my stay in Vienna at the reception of the hotel.
Booked and paid the hotel at hotels.com.
When we arrived, the girl in the reception claimed that it wasn't paid. I showed her the receipt from hotels.com, but she said she couldn't see the payment in the system.
I was told that I should present my credit card, but the amount for the stay would only be reserved.
A few days later the money was withdrawn from my account both from hotels.com and from Campus hostel.
It took three days before the money was back on my account.
Useless staff at the reception.
Rooms not very clean.
Building site across the street starting very early.
If you have the chance, stay somewhere else.
But Vienna is a beautiful city. Highly recommended.