Stolnica svetega Nikolaja (Ljubljana Cathedral), Ljubljana (must see)

Initially constructed in the Romanesque style during the 13th century, Saint Nicholas' Cathedral saw numerous renovations before being ravaged by fire in 1469. Its rebirth commenced in the early 18th century, with a complete transformation guided by the vision of the Italian painter and architect Andrea Pozzo. Frescoes by Giulio Quaglio, sculptures by Angelo Putti, and altars by Paolo and Giuseppe Groppelli breathed new life into the edifice, with Francesco Robba contributing an altar in the left transept adorned with angels. This marked the beginning of Ljubljana's Baroque era, setting the tone for the architectural evolution of the city.

The cathedral is recognizable by its octagonal dome crowning its eastern side, while two bell towers grace the western side, adorned with gilded apples containing various relics and inscriptions. These towers, completed in 1705–06, house six bells, including the second oldest one in Slovenia, dating back to 1326. The facades are decorated with niches housing statues of bishops and saints, Baroque frescoes, and ancient Roman tombstones. Other notable features include a side entrance adorned with a Gothic pietà and a sundial dating back to 1826, bearing a poignant Latin motto: "Nescitis diem neque horam" ("You don't know the day or the hour").

In 1996, bronze sculptured doors were installed to commemorate Christianity's 1250th anniversary in Slovenia and the visit of Pope John Paul II. The Slovene Door depicts the country's history, while the Ljubljana Door is decorated with portraits of 20th-century bishops.

Inside, much of the original Baroque splendor remains, including frescoes in the cupola depicting the Holy Spirit and angels, along with depictions of the coronation of the Virgin and the glorification of Saint Nicholas on the dome walls, surrounded by celestial beings.