Holm is best known for creating The Old Town Museum in Aarhus, Denmark, an open-air 'living' museum on the history of Danish life and architecture with a focus on the changes brought to urban life by the industrialization of the early 20th century and the development of the city through time.

[2] For the National Exhibition Holm reconstructed in the mayor's mansion a number of rooms from different time periods between 1597 and 1848.

[1] In spite of opposition in the museum-world Holm gradually expanded the museum which over time turned into a nationally unique institution with some 55 buildings from the end of the 1500s to the beginning of the 1800s.

He was married again in 1921, to Petra Julie Nielsen (1889-1983) who from that year became responsible for the textile collection in The Old Town, Aarhus, from 1938 as a museum inspector.

He was secretary for Samvirkende Jydske Turistforeninger for 12 years and was in the board of the Gamle Bygningers Bevaring.

He was also in the board of Turistforeningen for Aarhus og omegn and in 1903 he became member of the Kongelige Nordiske Oldskriftsselskab.