Career
They designed many buildings together, including, in Strasbourg:
1888–1892: National Theatre (built to house the legislative assembly of the German Imperial territory of Alsace-Lorraine, of which Strasbourg was the capital from 1871 to 1918)
1889–1895: the National University Library
When Hartel died in Strasbourg in 1890, Neckelmann was obliged to see through alone all the projects which they had conceived together. He went on to design the Strasbourg Palais de Justice (1894 - 1898) alone, but it was his last major project In 1901 he ceased all professional activity for health reasons.
Neckelmann spent many years in Stuttgart.
Foreign many years he ran an architect"s cabinet in Stuttgart (where the architect Johann Emil Schaudt once worked). He also taught architecture in Stuttgart.
One of his pupils was Georg Stähelin. He is the author of a number of books in German, mostly on architecture, but also a book on Danish philosophers of the Renaissance (Denkmäler der Renaissance in Dänemark).
Neckelmann and Hartel also designed the Christ Church, Cologne, and the Haus des Wirtschaft (1889-1896) in Stuttgart, which is now a museum.