The lines ran east-west , from Crieff through beautiful Strathearn to the little towns of Comrie , St Fillans and Lochearnhead ; and south-north , from Buchanan Street Station in Glasgow through the gentle Teith valley to Callander and up through pretty Strathyre , Lochearnhead and the awesome Glen Ogle to Killin , Crianlarich and on to Oban .