Dreikönigenpförtchen at St. Maria im Kapitol

The somewhat hidden Three Kings Gate at St. Maria im Kapitol (in the Cologne dialect “Dreikünnijepöötzche”) is considered to be the only one that has survived of the once many gates to the numerous walled monastic or abbey immunity districts of the medieval cathedral city.
The city’s jurisdiction ended at such walls and gates.

Very close to the large and magnificent Romanesque basilica of St. Mary in the Capital is this – comparatively small, but nevertheless noteworthy – highlight. It commemorates a very special episode in Cologne's history; for this, we must mentally transport ourselves back to the 12th century: On July 23, 1164, the then Archbishop Rainald von Dassel, returning from Italy, reached Cologne again and is said to have entered the city at this spot. This alone wouldn't be so historically worthy – but he had with him the relics of the Three Kings, brought back from Milan as war booty! A corresponding adoration scene is depicted above the Gothic pointed arch.

de.m.wikipedia.org/wiki/St._Maria_im_Kapitol