Most of the hotels in Florence, including several of the really luxurious ones, are stretched out along the Arno about 1 or 2 kilometers west of the important sights. That doesn't sound like much, but it is when taxis are scarce and expensive (a ride back from the center at night will cost 20,000 lire). I'm not sure that there was ever anything to see in this hotel ghetto but, if there had been, the heavy bombing of this area during WWII probably would have flattened it.
The best located hotel in the city is the Bernini Palace, one or two minutes on foot from the Uffizi Gallery, the Palazzo Vechhio and the Bargello. The hotel is centered between the Duomo and Ponte Vecchio, both of which are perhaps five minutes away on foot. Prices start at 290,000 lire per night including a huge buffet breakfast. The hotel is small, which means you'll get personal attention from the concierge, but there is no restaurant. Piazza San Firenze 29, 50122 Firenze, tel (055) 288 621, fax 268 272.
There are 65 hotels listed in the Michelin red guide to Florence. Two of them are marked in red as "especially pleasant." The Helvetia e Bristol is one of those two. Conveniently located a few blocks west of the Duomo, the rooms in this 19th-century palace are like a fairy tale with rich wall fabric, etchings, and antique furniture (it was remodeled in 1989 up to 5 stars). Beds are firm in the American style and most of the bathtubs have built-in Jacuzzis. You can have breakfast in the Wintergarden Room with its delicate stained-glass ceiling and feel the echoes of previous guests such as Igor Stravinsky, Luigi Pirandello, Bertrand Russell, and Enrico Fermi. This is the only Italian hotel in which I've managed to sleep without earplugs. Prices for the 52 rooms start at 362,000 lire. Hotel Helvetia & Bristol, Via dei Pescioni 2, 50123 Firenze, tel (055) 287 814, fax 288 353.
If you don't need the services of a big hotel, don't need a big room and still
want to be in the center, try the Hotel Della Signoria, Via Delle Terme 1, 50123
Firenze, tel (055) 239 6598, fax 216 101. The decor is stylishly modern. Prices
are from 130,000 per night in the low season and from 185,000 in the high season.
[Note: I've never stayed in this hotel; I just know about it because I went in to
take a picture from their terrace, which overlooks the street leading to the
Ponte Vecchio.]