Situated on the eastern section of the walls, Porta Pretoria provided the main access to the city of Augusta Praetoria. It was built in 25 BC after the defeat of the Salassians by Terenzio Varrone. It had three openings, which are still visible today: the central one for carriages and the side openings for pedestrians. The area inside the openings was used as a troop parade court, in its southern section, the land was dug up as far as the level of the ground during the Roman era.
On the outer facing openings you can still see the grooves from where the gates were lowered at night. The eastern facade still has some of the marble slabs that once covered the entire monument, on the inside it consists of blocks of puddingstone. In the Middle Ages there was a chapel dedicated to the Most Blessed Trinity resting against Porta Praetoria (now only an alcove of this remains), for many centuries, the same Porta Praetoria went by its name.
References:House of the Blackheads (Melngalvju nams) is a building situated in the old town of Riga. The original building was erected during the first third of the 14th century for the Brotherhood of Blackheads, a guild for unmarried German merchants in Riga. Major works were done in the years 1580 and 1886, adding most of the ornaments.
The structure was bombed to a ruin by the Germans June 28, 1941 and the remains demolished by the Soviets in 1948. The current reconstruction was erected from 1995 to 1999. Today the House of Blackheads serves as a museum and sometimes concert hall.