We stayed at the Grande Bretagne after a cruise in April 2012. The Hotel is a beautiful classic in a perfect location overlooking Syntagma Square. Most areas of Athens that are of interest to tourists are in walking distance or short cab ride. The interior is indicative of its position as the premier hotel in Athens for over a hundred years. The lobby is grandly furnished, as are the rooms. The staff could not have been more welcoming and helpful.
Our room - #706- I believe a deluxe room, while not extremely large, was beautifully furnished with a balcony with an astounding view. The bathroom was elegant.
The top floor has an open air restaurant with the same fantastic view of Athens and a swimming pool.

An incredibly beautiful hotel. The decadence and grandeur are hard to get over. Every time you return to the hotel and walk through the marble clad lobby you almost feel that you are staying in a palace. The service, facilities and location are also unbeatable. I highly recommend.

This hotel is stunning, the lobby, lobby bar, the rooms and then the rooftop! OMG! The view, the bar, the pool, lunch, dinner or drinks this is the definition of world class! When it is 100 degrees out side during the mid day stay in or by the pool and have a lovely lunch. Early mornings and evenings are for adventure out of the hotel but the mid day is all Grande Bretagne. Dinner and cocktails at sunset is the place to be. I hate gush but when something is this good I have to!

This is by far the most sumptuous hotel I have ever stayed in. The style is indeed "grand," with tons of polished marble, gorgeous mosaic floors, plush and beautiful carpets, extensive architectural finish on the walls, stairways, etc. Very posh.

The high tea (complementary for our stay, for some reason) was excellent, no cutting corners here. Superb scones and clotted cream, little sandwiches, and perfect tiny pastries, along with very good tea. As the other commentators have noted, breakfast is hard to beat. First, it is in the roof-garden with a view of the Acropolis! Second, the selection is extensive, probably 20 kinds of pastries including croissants, spinach pie, and lots of other things. Poached eggs in a little cup! Choices of honey! Wonderful cheeses, hams, yogurts, you name it.
There is also a spa, way more elaborate than most luxury hotels. A very good indoor swimming pool, the best gym I have seen in Europe or Asia, pedi/mani, massages of many kinds. This is a full service spa.
The location is also perfect, right on Constitution Square, across the street from Parliament which is beautifully lit up at night (as is the Acropolis, up the hill).
This is a very hard to top hotel.