I had a pleasant stay in Sweet Castle Apartment. Easy access to public transport (airport limpousine bus stop just next door, sinnonhyeon & eonju subway station, bus stops). Self check in and out. The apartment itself is very clean, no need to worry because there is a maid that will clean your room twice a week. It has modern interior design. Bed is extremely comfortable. Wifi is great. It provides complete equipment and amenities (microwave, cooker, frying pan, knives, towels, hairdryer, shampoo, washing machine, iron, etc.). There is 7/11 just outside the building. This area is very safe, even if you walk alone in the midnight. The owner Kevin is super helpful and very kind. I would definitely stay here again if I go to seoul!