The Holy Trinity Church was built in the years 1694–1702. Authority of the church and the seminary was the founder Prince Archbishop Johann Ernst von Thun. The church, together with the same time build St. John's Church (hospital church) the first building designed by Johann Bernhard Fischer von Erlach in Salzburg. He used as models various religious buildings in Rome—especially Francesco Borromini's Church Sant'Agnese in Agone in Piazza Navona. While the church is characterized by a discreet use of decorative elements, the entire structure conveys a palatial impression.
The church interior is a longitudinal oval room with four short barrel vaults with crossed arms, which are surmounted by the large drum dome. The monumental effect of the interior arises mainly from the simplicity of the building and the towering height of the dominant drum dome. The design is reminiscent of the inner shape of the Karlskirche in Vienna, which was the second sacral masterpiece by Fischer von Erlach.
The large dome fresco inside the church, Coronation of the Virgin, was executed by Johann Michael Rottmayr between 1697 and 1700. It was Rottmayr's first sacral dome fresco and shows the Coronation of the Virgin by the Holy Trinity with the assistance of the Archangel Michael, as well as other saints, angels, prophets, the ten holy popes, and the Church patriarch. The fresco sums up the Christian salvation and church history impressively together. The figures are grouped in concentrically arranged cloud banks. At the top lantern a Holy Spirit dove is present. The large dome fresco completes the impression of Baroque ecclesia triumphans, the triumphant Church, within the meaning of Baroque self-understanding of the church building.
The stucco work by Andrea Sallari and Johann Baptist Redi is limited in the main room to the capitals, and in the cross arms stucco boxes. The high altar was created in 1700 according to plans by Fischer von Erlach. It was revised in 1841, but was returned to its original state in 1947. The altar contains a sculptural group of the Trinity group with two adoring angels. The reliquary of St. Ernestus was designed in 1959 by Otto Prossinger. The two side altars contain magnificent life-size angels, which were designed by Fischer von Erlach and Michael Bernhard Mandl from 1700–02. The Marie miraculous image of the right side altar dates from the sixteenth century. The Baroque frame was carried out by Sebastian Stumpfegger.References:
Thank you Richard for comments and detailed information. The overall photo was incorrect as you mentioned and is changed now.
The overall photograph is not of the Holy Trinity Church, but rather of the Salzburg Cathedral [Dom zu Salzburg] about 1/3 mile south-ish across the Salzach. Its based on an original design by Vincenzo Scamozzi and implemented by Santino Solari. The project was complete by 1628, nearly 70 years before the Holy Trinity Church; and the two represent very different interpretations of Baroque architecture. The Cathedral is much more reminiscent of Palladio in its clearer geometry and combining of solid forms, evident both from the interior and exterior. The Holy Trinity is much more reminiscent of Borromini, which can be understood primarily from its interior.
The Porta Nigra (Latin for black gate) is the largest Roman city gate north of the Alps. It is designated as part of the Roman Monuments, Cathedral of St. Peter and Church of Our Lady in Trier UNESCO World Heritage Site. The name Porta Nigra originated in the Middle Ages due to the darkened colour of its stone; the original Roman name has not been preserved. Locals commonly refer to the Porta Nigra simply as Porta.
The Porta Nigra was built in grey sandstone between 186 and 200 AD. The original gate consisted of two four-storied towers, projecting as near semicircles on the outer side. A narrow courtyard separated the two gate openings on either side. For unknown reasons, however, the construction of the gate remained unfinished. For example, the stones at the northern (outer) side of the gate were never abraded, and the protruding stones would have made it impossible to install movable gates. Nonetheless, the gate was used for several centuries until the end of the Roman era in Trier.
In Roman times, the Porta Nigra was part of a system of four city gates, one of which stood at each side of the roughly rectangular Roman city. The Porta Nigra guarded the northern entry to the Roman city, while the Porta Alba (White Gate) was built in the east, the Porta Media (Middle Gate) in the south, and the Porta Inclyta (Famous Gate) in the west, next to the Roman bridge across the Moselle. The gates stood at the ends of the two main streets of the Roman Trier, one of which led north-south and the other east-west. Of these gates, only the Porta Nigra still exists today.
In the early Middle Ages the Roman city gates were no longer used for their original function and their stones were taken and reused for other buildings. Also iron and lead braces were broken out of the walls of the Porta Nigra for reuse. Traces of this destruction are still clearly visible on the north side of the gate.
After 1028, the Greek monk Simeon lived as a hermit in the ruins of the Porta Nigra. After his death (1035) and sanctification, the Simeonstift monastery was built next to the Porta Nigra to honor him. Saving it from further destruction, the Porta Nigra was transformed into a church: The inner court of the gate was roofed and intermediate ceilings were inserted. The two middle storeys of the former gate were converted into church naves: the upper storey being for the monks and the lower storey for the general public. The ground floor with the large gates was sealed, and a large outside staircase was constructed alongside the south side (the town side) of the gate, up to the lower storey of the church. A small staircase led further up to the upper storey. The church rooms were accessible through former windows of the western tower of the Porta Nigra that were enlarged to become entrance doors (still visible today). The top floor of the western tower was used as church tower, the eastern tower was leveled, and an apse added at its east side. An additional gate - the much smaller Simeon Gate - was built adjacent to the East side of the Porta Nigra and served as a city gate in medieval times.
In 1802 Napoleon Bonaparte dissolved the church in the Porta Nigra and the monastery beside it, along with the vast majority of Trier"s numerous churches and monasteries. On his visit to Trier in 1804, Napoleon ordered that the Porta Nigra be converted back to its Roman form. Only the apse was kept; but the eastern tower was not rebuilt to its original height. Local legend has it that Napoleon originally wanted to completely tear down the church, but locals convinced him that the church had actually been a Gaulish festival hall before being turned into a church. Another version of the story is that they told him about its Roman origins, persuading him to convert the gate back to its original form.
In 1986 the Porta Nigra was designated a World Heritage Site, along with other Roman monuments in Trier and its surroundings. The modern appearance of the Porta Nigra goes back almost unchanged to the reconstruction ordered by Napoleon. At the south side of the Porta Nigra, remains of Roman columns line the last 100 m of the street leading to the gate. Positioned where they had stood in Roman times, they give a slight impression of the aspect of the original Roman street that was lined with colonnades. The Porta Nigra, including the upper floors, is open to visitors.