Monaco Cathedral, Monte-Carlo (must see)

The Monaco Cathedral, but sometimes also called Cathedral of Our Lady Immaculate or Saint Nicholas Cathedral, Monaco Cathedral, is the cathedral of the Roman Catholic Archdiocese of Monaco, where many of the Monaco royals were buried, including Grace Kelly and more recently, Rainier III.

The cathedral was built in 1875–1903 and consecrated in 1911, and is on the site of the first parish church in Monaco built in 1252 and dedicated to Saint Nicholas. Of note are the retable (circa 1500) to the right of the transept, the Great Altar and the Episcopal throne in white Carrara marble.

Pontifical services take place on the major religious festivals, such as the Feast of Sainte Dévote (27 January) and the national holiday (19 November). On feast days and during religious music concerts, one can hear the magnificent four-keyboard organ, inaugurated in 1976.

From September through June, the singers of the Cathedral Choir School sing during Mass every Sunday at 10am. Mass is also celebrated here each year on 6 December, when primary children gather for a joyful remembrance of Saint Nicholas' life.

If you're a Princess Grace buff, there's a nice memory of her and Prince Rainier here.
The interior is beautiful and excess-free. The cathedral's organ is an amazing sight to see.