Photogrammetry in practical use

3D model of the archaeological site

 

Model by: Atlas 3D – photogrammetry Poland

 

In the northwestern part of the Kraków Archaeological Museum garden, right next to Poselska Street, archaeologists have uncovered a relic of a 19th-century block sewer. This is part of the work accompanying the thorough modernization of the museum’s historic headquarters—an investment being carried out to celebrate its 175th anniversary. The discovery was documented in the form of a photogrammetric 3D model, which I prepared based on photos from a drone and digital cameras. You can see the results at the end of this post.

What is a block sewer?

The discovered sewer is a classic 19th-century engineering structure. A fragment with vertical side walls, a barrel vault, and a concave bottom has been preserved. It was made of limestone, sandstone, and brick—likely obtained from the demolition of Kraków’s city walls. Interestingly, the structure also shows later repairs using cement and machine-made brick.

The interior of the sewer is approximately 1.20 m wide and 1.30 m high. The bottom was lined with so-called “cat’s heads” (kocimi łbami)—distinctively hewn limestone. Most of the elements were originally joined with lime mortar, which facilitates their dating.

A brief historical background

The liquidation of block sewers in Kraków took place mainly between 1958–1967 and in 1972. The work, performed by miners from Bytom, involved filling the inactive sewers with filter sand—a method also used in mining. The channels were segmented with concrete partitions, which increased ground stability.

Unfortunately, the old city sewer plans were destroyed by the Germans during World War II, which today significantly complicates the identification of such relics.

A paleontological surprise

During the work, a unique curiosity was also uncovered—a limestone slab with a visible fossil of an ammonite, a cephalopod that lived in the seas of the Mesozoic period (approximately 240–65 million years ago). The builders clearly took care not to damage this fossil. Today, it serves not only as a decoration but also as a valuable geological element.