This place is just great. It is also our first AIRBNB experience. It looks exactly like the photos and we found it very clean and totally comfortable. Marina was waiting for us right on time when we arrived the first week of April. There is lots of storage space in the downstairs (main) bedroom and everything is tastefully decorated. The building itself is quiet. The are three floors with a front and rear unit on each floor. If you need to do laundry there is a roof top terrace with clothes lines that works great. When you get here explore all the unlocked cabinets to find things like clothes pins, broom, mop, etc. The bedroom has a heavy door that blocks out any street noise very effectively. It is very well insulated. Although in was 85 degrees (F) outside it was cool and comfortable inside.
Regarding upstairs beds: There is no railing so you have to be careful of the 6 foot drop. Also no railing on the narrow stairs. If someone is using these beds they are subject to the street noise and have to go through the downstairs bedroom to get to the bathroom. With just the two of us it seemed the best situation.
We were originally looking at a place on Plaza Nueva. Castellar is much more quiet and laid back. It's nice to take the 10 minute walk and leave all the commercial hustle and bustle behind.
There is a large Dia supermarket very near. Just go out the front door, turn right and right again and you will see it on the left in the small plaza. To get to the major central sights: Go out the door, turn right and then left on Calle Feria (all street names above the door on the corner). Take a left on Feria and follow it more or less straight to the big Parasol thing (you really can not miss it). This puts you on Larana. Turn right. All the streets on your left are the major shopping streets between Larana and the Cathedral. If you turn left (south) down Cuna you will pass after one block the best authentic Flemenco show at Casa de la Memoria. This is non touristy (even though filled with tourists) in a very intimate venue and was just amazing. Or you can go west to Sierpes or one more to Velasquez Tetuan. They are all busy shopping streets that lead to the Plaza Nueva, the Cathedral (and Alcazar).
Now if you go out the door of the appartment and turn left you get to Plaza San Marcos. A good little tapas bar and some smaller markets. Turning right on Bustos leads you again to Larana and Plaza Ponce de Leon. Bear left across the street of Plaza Padre Jeronimo and the great Catalina Restaurant (bottom floor of red brick hotel).
With a good map you will have no trouble exploring the winding streets of Macarena.