When I stayed at the Abba Garden in 2007, it was a fairly new hotel. The rooms are huge and clean, the beds bigger than they were in any other hotel I stayed in on my tour of Europe, and the pool was great. Technically it isn't in the city center, but depending on where you're coming from a taxi is only 12 (from the Placa de Catalunya) to 20 (from Port Olympia) euro and the hotel is convenient to a bus stop as well. The only downside I really found was that because the hotel was so new, a lot of the taxi drivers didn't know where it was--we kept having to use the hospital across the street as a reference point. However, I can only assume that in the few years since I stayed here the Abba Garden's location has become common knowledge.