Kevin Y.
Yelp
Relatively high-class restaurant right next to the Real Madrid stadium. You can get a pretty spectacular view of the Santiago Bernabeu Stadium football field, but you should request a table by the window to guarantee it.
Food-wise, most of the dishes are good, but a little bit overpriced. There was not really anything on the menu (aside from the desserts) that I hadn't already seen before at every other Spanish restaurant I've been to. Many of the members of my party decided to get the solomillo, and while they said that the dish tasted delicious, they were a bit disappointed because the portion seemed pretty small (when compared to the other solomillos they've had in Spain). I got the entrecot for dinner, and it was a very hearty and generous steak with a solid portion of fat included. I'm personally a big fan of steak fat, but if you're not, I do warn you that it probably makes up 30 - 40% of the dish.
As for the restaurant itself, the atmosphere is a bit more upscale than I've been used to here in Madrid. While I do not believe that there is an official dress code, long slacks and a collared shirt seem to be the norm here. Just something to keep in mind before you walk in wearing shorts and a t-shirt.
For the novelty of being able to eat a nice meal at the Real Madrid football stadium (and getting a great view of the field itself), I'd have to say that making a trip to Puerta 57 is worth the money.