Cons:

Adler Spa Thermae falsely advertises on its website and third party booking platforms that the rooms have air conditioning. Instead, the rooms are heated and cooled using irradiation panels in the floor and ceiling which were limited to increasing or decreasing the temperature by 3 degrees celsius from a 23 degree celsius starting point. It is an interesting concept, but the room did not cool quickly and I was too hot when going to bed. Luckily, the front desk provided a portable A/C unit, but it required us to keep our ground floor slider door open all night for the hose and vent to go outside. If I would have known that the rooms did not have air conditioning, I would have booked somewhere else as this is a mandatory requirement for me.

The spa does not have very good customer service. They sent an e-mail to me prior to my stay to ask if I wanted a personal consultation before my visit to go over the spa menu. I responded asking for one, but they never e-mailed or called me back. They encourage you to book spa treatments in advance, but then they have a an inflexible cancellation policy. One one of our days we decided in the morning around 10am that we didn't need our 5pm massages anymore, but they wouldn't allow us to cancel them and ended up charging the full amount to our room despite us not receiving any massage services.

We had a noise issue with the floor above us. They were stomping around their room late at night which made it hard to sleep. We called the front desk at midnight and they said they would call the room above us to ask them to be quieter. I would recommend the top floor for anyone concerned about noise.

There was a random fire alarm at 3:30am on our last night due to a system malfunction.

Pros:

The front desk staff is amazing. They are very friendly and helpful and helped to resolve issues as they came up. They literally saved our stay by providing the portable A/C unit and helping us get a refund from the spa on massages they wouldn't let us cancel.

The half board is very affordable at only 25 euros per night per person which gives you an all inclusive access to a very classy dinner each night. We didn't realize this was more of a formal attire dinner place, so make sure you have some nice dining clothes with you. We saw a lot of suit jackets/ blazer and nice dresses.

If you get the half board package you will never be hungry as you will get breakfast, afternoon desserts and dinner every day. You could buy lunch at the restaurant on site, but we never needed to because we were so full.

Suggestions to the hotel:

Clarify on your website and third party booking platforms, that the property does not have air conditioning. I would suggest labeling the air conditioning as "other" and provide the description of what it actually is.

The spa customer service could be improved. More flexible cancellation policies would make the stay much more enjoyable.