While still a student, he participated in decorating the residence of Hermann Ernst Freund (1786–1840), an academy professor of sculpture, in the former Supply Building on Slotsholmen.

This gave him the opportunity to study Pompeian art and Raphael's works at the Vatican.

The following summer, he also went to Naples, Pompeii and Capri where he lived and worked with Christen Købke and fellow Danish painters Constantin Hansen and Jørgen Roed.

[1][5] Back in Denmark in 1841, Hilker's career was launched when he received an important commission from architect Michael Gottlieb Bindesbøll (1800–1856) to decorate rooms in Thorvaldsens Museum.

These projects displayed antique motifs either directly or in the modified Neo-Renaissance form and frequently involved collaborations with other artists, especially Constantin Hansen.