Saint Basil Cathedral (Moscow, Russia)

Basil of Caesarea, also called Saint Basil the Great, (330– January 1, 379) (Greek: Άγιος Βασίλειος ο Μέγας) was the bishop of Caesarea Mazaca in Cappadocia, Asia Minor (modern-day Turkey). He was an influential 4th century Christian theologian and monastic. Theologically, Basil was a supporter of the Nicene faction of the church, in opposition to Arianism on one side and the followers of Apollinaris of Laodicea on the other. His ability to balance his theological convictions with his political connections made Basil a powerful advocate for the Nicene position.
In addition to his work as a theologian, Basil was known for his care of the poor and underprivileged. Basil established guidelines for monastic life which focus on community life, liturgical prayer, and manual labor. Together with Pachomius he is remembered as a father of communal monasticism in Eastern Christianity. He is considered a saint by the traditions of both Eastern and Western Christianity.
Basil, Gregory of Nazianzus, and Gregory of Nyssa are collectively referred to as the Cappadocian Fathers. The Eastern Orthodox Church and Eastern Catholic Churches have given him, together with Gregory of Nazianzus and John Chrysostom, the title of Great Hierarch. The Eastern Orthodox Church and the Roman Catholic Church have also named him a Doctor of the Church. He is also referred to as "the revealer of heavenly mysteries" (Ouranophantor).

source: en.wikipedia.org/wiki/Basil_of_Caesarea

Duomo, Milan Cathedral (Milan, Italy)

Milan Cathedral (Italian: Duomo di Milano; Milanese: Domm de Milan) is the cathedral church of Milan in Lombardy, northern Italy. Dedicated to Santa Maria Nascente (Saint Mary Nascent), it is the seat of the Archbishop of Milan, currently Cardinal Dionigi Tettamanzi.
The Gothic cathedral took five centuries to complete. It is the largest Gothic cathedral and the second largest Catholic cathedral in the world.

source: en.wikipedia.org/wiki/Milan_Cathedral

Paraportiani Church (Mykonos, Greece)

The Church of Panagia Paraportiani (Greek: Εκκλησία της Παναγίας Παραπορτιανι) is situated in the neighbourhood of Kastro, in the town of Chora, on the Greek island of Mykonos. Its name literally means "Our Lady of the Side Gate" in Greek, as its entrance was found in the side gate of the entrance to the Kastro area.
The building of this church started in 1425 and was not completed until the 17th century. This impressive, whitewashed church actually consists of five other churches attached all together: the four churches (Saint Estathios, Saint Sozon, Saints Anargyroi and Saint Anastasia) are all on the ground and constitute the base of the fifth church that has been built on top of them. This architectural spottiness has made Panagia Paraportiani the most photographed church on Mykonos.

source: en.wikipedia.org/wiki/Paraportiani

Sagrada Familia (Barcelona, Spain)

The Basílica i Temple Expiatori de la Sagrada Família (English: Basilica and Expiatory Church of the Holy Family, Spanish: Basílica y Templo Expiatorio de la Sagrada Familia; Catalan pronunciation: [səˈɣraðə fəˈmiɫiə]), commonly known as the Sagrada Família, is a large Roman Catholic church in Barcelona, Catalonia, Spain, designed by Catalan architect Antoni Gaudí (1852–1926). Although incomplete, the church is a UNESCO World Heritage Site, and in November 2010 was consecrated and proclaimed a minor basilica by Pope Benedict XVI.
Though construction of Sagrada Familia had commenced in 1882, Gaudi took over in 1883, transforming the project with his architectural and engineering style — combining Gothic and curvilinear, Art Nouveau forms with ambitious structural columns and arches.

source: en.wikipedia.org/wiki/Sagrada_Família