The Castle Inn offers large motel-style rooms in a central location. If what you want is simple and tidy, then the Castle Inn might work well for you. The rooms are very clean, but the overall look of the place is somewhat dated and shabby.
The Castle Inn offers a few nice amenities. Rooms are equipped with both refrigerators and microwaves. Though there is not an on-site restaurant, they have arranged for "room service" through a near-by budget diner. You will also find that you receive all basic cable channels through their television service. Each room also has independently-controlled heat and A/C, which can be nice when SF's weather varies.
The drawbacks are due mostly to the physical plant of the building. It is an old four-level motel with open-air hallways. Because of the set-up, each room has one medium-size window that looks out onto the adjacent building. Therefore, the rooms feel pretty dark, which is not helped much by the small lamps and CFL bulbs. The indoor decor is dated, and the public spaces look a little shabby, from stained indoor-outdoor carpeting on the stairs and halls to scraggly geraniums on the stair landings. As well, though the Inn offers breakfast, it is hosted on a small counter within the main office; you have to be patient with the line to get your milk and cereal or granola bar.
The location is good, but not great. You can easily take a bus line north on Van Ness to the waterfront or south toward the Castro. The closest BART stop is about 1.5 miles away, so a cab or shuttle is your best option to and from the airport. The Inn is convenient to Nob Hill and Polk Gulch if you're looking to browse a few shops or grab a bite to eat. However, these are not the most exciting areas to go out and about in San Fran.
In short, Castle Inn is serviceable, but nothing fancy. The overall value varies, depending on time of year. My king room ran about $200 per night in the last week of June. If I had been able to book a room in town earlier, I likely could have been able to stay at a three-star establishment for the same price.
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