Berzabuena writes:
... a room with a twin bed would most likely be denominated "cama de matrimonio".
NOT! A
cama de matrimonio is a full size (double) bed. But they tend to be smaller than in the U.S. so you might be more comfortable with a 'twin double' (
una habitación con dos camas) or a 'double double' (two double beds). Queen-size beds are very rare in Spain.
Most Madrid hotels (3-star or above) will have twin-doubles and double-doubles available.