The nearest airport is Geneva (GVA), from which Annecy may be reached through public transport (bus or train). Bus companies include:
• Line 272 - Annecy / Genève Aéroport
• Flixbus - Annecy / Genève (either Aéroport or downtown)
• BlaBlaCar Bus - Annecy / Genève downtown
Trains Annecy - Genève are provided by Léman Express. Beware that direct connections take about 1h30min (but may be very comfortable otherwise).
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Detailed information on accessing LAPTh from downtown Annecy can be found at this page. In short, LAPTh can be reached by public transport from central Annecy through bus lines 1 or 4, getting off at the 'Campus' stop. Single bus tickets (1.50 €) can be bought from the bus driver. In alternative, booklets of 10 tickets (11.50 €) can be bought from the Sibra office (on the train-station square) or other selling points (e.g. bar-tabac shops, for a list see https://www.sibra.fr/en/points-de-vente).