Madrid is impossible to see whole in one day. You need at least three. In my case, I was in this city just for 20 hours. The most interesting thing I have visited was the Prado museum. I was not able to imagine so many paintings and sculptures concentrated in one building before coming here. Here is a list of artists whose creations are put in front of eyes of the public: Titian, El Greco, Durer, Bosch, Van der Weyden, Raphael, Goya, Murillo, Ribera, Velaquez, Rubens, Rembrandt, Poussin, Watteau, Tiepolo, Mengs, Lorrain, Ranc, van Loo, Bouts, Memling, Brueghel, Van Dyck, Cranach, Grien, Angelico, Mantegna, Boticelli, Tintoretto, Veronese, Caravaggio, Gentileschi, Leone, Pompeo Leoni. On the opposite side to the museum You can see many nice trees and brushes that come from all parts of the world. This place is called Real Jardín Botánico .
Other nice spots are Plaza de Oriente with statues of all kings of Spain in its whole history of existence and Plaza Mayor which has in its centre statue of Felipe II, one of the most well-known Spanish kings.
Tens kilometres to south from Madrid lies Toledo, in my opinion the most beautiful city out of all I have seen during my stay in Spain.