https://rogerfarnworth.wordpress.com/20 ... rovence-73
The centre piece of this section of the line is the 3.5 kilometre long tunnel which links the valleys of the Verdon and the Vaire together - the Tunnel de la Colle Saint Michel.
The railway line between Meailles and Thorame-Haute was on the last stretch of the line from Nice to Digne to be built. The length involved was that between Saint-André-de-Méouilles and Puget-Théniers.
Work began in January 1900 on the final 27km of the line. The tunnel boring took a number of years to complete. Steady progress was made on the tunnel. The project had a significant setback when, in April 1909 part of the land mass above the proposed location of the station at Thorame-Haute collapsed onto the site of the station engulfing the part built buildings and platforms. Stabilisation of the mountain required the construction of a 114 metre long, 33 metre high retaining wall. The wall was 1.5 metres thick and reinforced by 7 buttresses. 
The station was opened to travellers on 3rd July 1911  with the inauguration of the full line taking place on 6th August 1911. The station at Thorame-Haute quickly became a significant tourist destination providing access to some high quality hotels in the upper reaches of the Verdon valley. A wealthy clientele travelled from the Côte d'Azur to access such hotels as the Alp'hôtel de Beauvezer, and the Fontgaillarde in Thorame-Haute.