Upvote:3
You can store it there, it will also be cheaper too since you will probably get a locker at the bath for your valuble items anyway, so no need to duplicate!
Upvote:13
The official website of the baths note that the lockers are size "120x30x65 cm", and that larger bags can be stored within the cabin.
Cabins are actually personal changing rooms that you get assigned to, and you open with a wristband so it is secure. As stated on their website
"The size of the cabin can easily hold a standard suitcase or a backpacker style bigger backpack"
Here's a photo so you can fully appreciate how big the cabins are!