Alt St. Katharina, Romanesque religious monument in Niehl, Germany.

Alt St. Katharina is a Romanesque basilica in Cologne-Niehl, first built in the 12th century with a west tower and three aisles. Its light tan stone walls are supported by buttresses, and the nave has a dark slate roof with three large arched windows. A steep slate pyramid tops the square tower, and a small rounded apse closes the east end.

Niehl was first documented in 927, and by 1236 a chapel belonging to the Kunibert monastery stood here; its main altar was consecrated to St. Catherine in 1260. The present church was built in the 12th century as a three-aisled Romanesque basilica with a west tower. The choir was rebuilt in Gothic style around the mid-13th century, the nave was vaulted around 1400, and the north aisle was reconstructed on old foundations in 1894, the same period when the larger Neu-St. Katharina was built to replace it as parish church.

Locals call the church "Niehler Dömchen", the little cathedral of Niehl. It is open on Friday late afternoons for Mass and on Wednesday mornings for a school service of the neighbouring primary school; volunteers aim to open it more often. Inside, a pulpit bearing an image of St. Catherine and the year 1622 survives.

Alt St. Katharina stands directly on the Rhine bank beyond the Niehler Damm, east-facing, in Cologne-Niehl. It is open Friday late afternoon for Mass and Wednesday morning for a school service of the neighbouring primary school; volunteers are working toward more frequent opening.

Locals call the church "Niehler Dömchen" (little cathedral of Niehl). Its main altar was consecrated in 1260 by auxiliary bishop Heinrich I. von Montfort to Saint Catherine. The pulpit carries her image and the year 1622; a crowned Madonna from the 16th century also survives inside.