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:The Broch of Clickimin is a large and well preserved, though somewhat restored broch near Lerwick. Originally built on an island in Clickimin Loch (now increased in size by silting and drainage), it was approached by a stone causeway. The water-level in the loch was reduced in 1874, leaving the broch high and dry. The broch is situated within a walled enclosure and, unusually for brochs, features a large 'blockhouse' between the opening in the enclosure and the broch itself. Another unusual feature is a stone slab featuring sculptured footprints, located in the causeway which approached the site. Situated across the loch is the Clickimin Leisure Centre.