3408, 3417, 3445 SPAIN (Community of Madrid) - Royal Palace of Madrid

3408 Royal Palace of Madrid and Almudena Cathedral

Located on Bailén Street, in the western part of downtown Madrid, east of the Manzanares River, the Royal Palace of Madrid is the official residence of the Spanish royal family, although now only used for state ceremonies. The palace has 135,000 square metres of floor space and contains 3,418 rooms, being the largest functioning royal palace and the largest by floor area in Europe. The last monarch who lived continuously in the palace was King Alfonso XIII, although Manuel Azaña, president of the Second Republic, also inhabited it.

3417 Royal Palace of Madrid - Gasparini Room (18th-19th centuries)

The interior of the palace is notable for its wealth of art and the use of many types of fine materials in the construction and the decoration of its rooms. It includes paintings by artists such as Caravaggio, Juan de Flandes, Francisco de Goya, and Velázquez, and frescoes by Giovanni Battista Tiepolo, Corrado Giaquinto, and Anton Raphael Mengs. Other collections of great historical and artistic importance preserved in the building include the Royal Armoury of Madrid, porcelain, watches, furniture, silverware, and the world's only complete Stradivarius string quintet.

3445 Royal Palace of Madrid - The kitchen of Ramillete 

The palace is located on the site of a 9th-century Alcázar (Muslim-era fortress), near the town of Magerit, constructed as an outpost by Muhammad I of Córdoba and inherited after 1036 by the independent Moorish Taifa of Toledo. After Madrid fell to King Alfonso VI of Castile in 1083, the edifice was only rarely used by the kings of Castile. In 1329, King Alfonso XI of Castile convened the cortes of Madrid for the first time. King Felipe II moved his court to Madrid in 1561.

The old Alcázar was built on the location in the 16th century. After it burned 24 December 1734, King Felipe V ordered a new palace built on the same site. Construction spanned the years 1738 to 1755^[6] and followed a Berniniesque design by Filippo Juvarra and Giovanni Battista Sacchetti in cooperation with Ventura Rodríguez, Francesco Sabatini, and Martín Sarmiento. King Carlos III first occupied the new palace in 1764.

About the stamps
On the postcard 3408

Designed by Greg Breeding, the first stamp, World War I - Turning the Tide (Forever priced at the First-Class Mail rate), was issued on July 27, 2018, to pays tribute to the sacrifice of American soldiers and millions of supporters on the home front who experienced WWI. Entering WWI (1914-1918) in its later stages, the United States helped turn the tide of war in favor of the Allies. The stamp art features a close-up of a member of the American Expeditionary Force holding the U.S. flag. Barbed wire can be seen in the background, as well as an airplane in flight and smoke rising up from the battlefield. The artwork was painted in airbrush on illustration board, a technique that evokes the propaganda posters used during WWI.

The second stamp, depicting grapes, is part of the series of definitives stamps, Fruits, about which I wrote here.

The last stamp, depicting a dutch shepherd, is part of the series of forever stamps Military Working Dogs, about which I wrote here.

On the postcard 3417
The first stamp, depicting grapes, is part of the series of definitives stamps, Fruits, about which I wrote here.

The second and the third stamp are part of the series State and County Fairs, issued on July 25, 2019. The colorful se-tenant stamps - one scene across four stamps - celebrate the fun of America's state and county fairs. The stamp on the far left shows farmers unloading produce behind a white fence. In the second stamp, a child holding a chicken sits atop the same fence, with carnival rides - a Ferris wheel and merry-go-round - in the background. Those rides can be seen in the third stamp, where some fairgoers admire the livestock behind the fence while others walk, balloons in hand, toward a sweets stand. The last stamp shows children at the stand buying treats from the vendor. The art director was Greg Breeding, and Mike Ryan designed the stamps with original art by Mick Wiggins. The State and County Fairs stamps are being issued as Forever stamps and will always be equal in value to the current First-Class Mail 1-ounce price.
1 - It's on the postcard 3417
2 - It's on the postcard 3417

On the postcard 3445
The first stamp, depicting grapes, is part of the series of definitives stamps, Fruits, about which I wrote here. About the second stamp, World War I - Turning the Tide, I wrote above. About the last stamp, which celebrate the Year of the Rat, I wrote here.

References
Royal Palace of Madrid - Wikipedia

Sender 3408, 3417, 3445: Denise
3408, 3417: Sent from West Babylon (New York / United States), on 15.01.2020
Photo 3408: Xavier Duran
3445: Sent from Glen Head (New York / United States), on 18.01.2020