Incredibly central and surprisingly quiet (note we stayed Sunday/Monday so might not be peak busy at next door pub/restaurant) right in the middle of Grassmarket. Although you can't view the castle from the apartment, about 1 minute walk away you can see it. Sightseeing bus stops just outside and Sainsbury's metro nearby for supplies. The flat is basic but warm, light and bigger than pictures suggest. Boiler and extractor were a bit noisy but everything was clean, comfortable and perfect base for exploring. Only minor quibble was I had to chase up check in twice on the day of arrival although I was assured there was an issue with phone signal and our experience was an exception. Once we had the code for lock box it was super easy to get in. Fab traditional sweetshop opposite too.