Most notably he was the founder of Rhaetian Railway and patron of the tourism destination Davos.

In 1865, he was designated to become the director of the bank in a newly opened subsidiary in London, United Kingdom.

In 1867, due to the lung disease of his wife, they decided to relocate to Davos, Switzerland.

Most notably, Holsboer served as the first president of Davoser Gesellschaft der Elektrizitätswerke (electrical power supply company), and under his initiative the Bank of Davos as well as the Rhaetian Railway was founded.

After his wife died from tuberculosis he would remarry to Swiss Ursula Büsch, a native of Davos, in 1868.