Take the train from the airport to Roma Termini (14 euros) and then a cab to the apartment (15 euros for 3 people with luggage). Despite its great location, the apartment is incredibly quiet. 1 minute walk from the Trevi Fountain, 2 minute walk to the Spanish Steps, 0.9 miles to the Colosseum and a ~20 min walk to the Vatican. The recommendations left by the host for good local restaurants are spot-on.