The third anchor in the golden art trio, a landmark of old Madrid, is the Hospital de San Carlos (c/ Santa Isabel 52), which now houses the Centro de Arte Reina Sofia.
The Hospital de San Carlos doesn't house anything.
mnli hypothesis: The Hospital de San Carlos doesn't house anything. premise: The third anchor in the golden art trio, a landmark of old Madrid, is the Hospital de San Carlos (c/ Santa Isabel 52), which now houses the Centro de Arte Reina Sofia.