My girlfriend and I visited this apartment during our 4-day stay in BA and I can really recommend everyone to use Ralf and his apartments - especially the "Sunset Luxury 20th floor studio" due to the incredible view!
When we arrived Marcelo (Ralfs co-worker) gave us a 1,5hrs speech about BA about what to do doing our stay, which included many great tricks we wouldn't have got to know without knowing someone from BA ourselves. Extremely good service I think! :)