Raquel really enjoys going to Postcrossing meeting, I mean, who doesn't?! In the last days of May she has been to 2 meetings, one here in Portugal and then one in Trier, Germany. She sent me a south view of Porta Nigra; back in 2008 Anna sent me a view of the north side.
In 1986 Porta Nigra was designated as part of the Roman Monuments, Cathedral of St. Peter and Church of Our Lady in Trier UNESCO World Heritage Site.
The Porta Nigra is a magnificent 2nd-century Roman city gate in Trier. It was given its name (which means "black gate") in the Middle Ages because of its weathered color.
The oldest defensive structure in Germany, the Porta Nigra was erected in about 180 AD when the Roman city was surrounded by walls. Trier was a Roman colony from the 1st century AD and then a great trading centre beginning in the second century. It became one of the imperial capitals under the Tetrarchy at the end of the 3rd century, and became known as the "second Rome."
The Porta Nigra is the only one of four Roman gates that still stands in Trier; the others were gradually pillaged for their stone and iron. The Porta Nigra survived because it was used as the humble residence of a hermit monk named Simeon for seven years (1028-35). After his death he was buried in the gate and the structure was transformed into the two-story Church of St. Simeon (lay church on the bottom, monastery church on top).
Napoleon destroyed the church in 1803, but the 12th-century Romanesque apse survived and the entire structure has been restored to its medieval appearance. - in: http://www.sacred-destinations.com/germany/trier-porta-nigra