To the north of Siwalai Garden once stood the palace arsenal. King Rama V
ordered it pulled down to make way for a two-storey European building with grey slate roof. He called it Phra-Thinang Pha numatchamrun and
planned to give it to the Crown Prince, H.R.H. Prince Maha Vajirunahis who died before it was completed. When H.R.H. Prince Vajiravudh
became Crown Prince he did not stay here. Only after his ascension to the throne did he come to stay here occasionnally and changed its
name to "Boromphiman", after building of that name which had been pulled down.
Prior to his Coronation, King Rama VII came to stay here for some time. King Ananda Mahidol (Rama VIII) took residence here
together with his younger brother and mother when they returned from Europe in 1946. King Ananda Mahidol passed away in this mansion.
Since his tragic death it has been little used. It has now been repaired and serves as a guest house for visiting royalty and heads of states.