Gerard and Byron’s apartment is in a good location in the hip Lavapies barrio in Madrid. Most of the city’s major tourist attractions, including the Big 3 museums, are within walking distance. The apartment is small but has a comfortable bed, good WiFi, a TV and a washing machine.
The only negative is that the unit is located in the interior of the building, meaning that the only natural light comes from the ventilation shaft. If you’re not planning on being in the apartment very much, then it shouldn’t be that big of an issue.