The Mountain slide in the Marble Hall (also called the Mountain Hall) at the Alexander Palace,Tsarskoe Selo.
Tsar Nicholas l of Russia installed a great slide which took up almost half the room.
In Russia slides are called “mountains” thus the name.
Also in the photo is the miniature Mercedes made for the Tsarevich Alexei Nikolaevich Romanov of Russia.

Princess Ekaterina Mikhailovna Dogorukaya, “the Odalisque” of Alexander II

At 3 p.m. on 6 July, at Alexander I´s field church in Tsarskoe Selo, the tsar, in pale-blue Hussars uniform, and Katya, in a wedding gown, were married by Father Ksenophont Nikolsky. … After a small supper the couple took a carriage ride around the park. Then Alexander signed a decree: “Having entered … into a lawful marriage with Princess Ekaterina Dolgorukaya, we command her to be named Most Serene Princess Yurievskaya with the same name given to the children.” He feared that “Russian and History will never forgive me,” yet “That stone which oppressed his heart had been lifted,” wrote Katya “and [he was] as happy as a being yould ever be.”

Next morning, he told Count Loris: “I know how loyal you are to me. Now you must be loyal to my wife and children.” Loris started to consult Katya, who afterward reflected, “The outstanding minister understood what a valuable ally the princess was as wife of the tsar.” As the family learned of the secret marriage, he justified himself to his sister, Ollie, queen of Württemberg: Katya “preferred to rennounce all the social amusements and pleasures desired by young ladies and has devoted her entire life to me”, but “without interfering in any affairs, she lives only for me, dedicated to bringing up the children.” Sasha [future Alexander III] thought the marriagea “forever ruined all the dear good memories of family life”. As he later wrote to [his wife], it was “The start of these troubled times, this living nightmare.”

S.S. Montefiore: The Romanovs

Grand Duchesses Maria and Anastasia Nikolaevna Romanova of Russia in a carriage with their mother Empress Alexandra Feodorovna of Russia in front of their infirmary at the Feodorovsky Gorodok, Tsarskoe Selo.

The Children’s Cottage on the Children’s Island at thd Alexander Park at Tsarskoe Selo.Built for the children of Tsar Nicholas l of Russia.

Grand Duchesses Tatiana Nikolaevna Romanova of Russia (left) and Grand Duchess Olga Nikolaevna Romanova of Russia (right) with wounded soldiers at the Hospital at Tsarskoe Selo in 1915.

Front and back of the postcard sent by the Empress Alexandra Feodorovna of Russia to the Infirmary at Tsarskoe Selo from Tobolsk.Dated 14 November 1917.