By plane
Arrive at Chandigarh airport. There are many connecting flights from Delhi/Mumbai/Bangalore/Pune to Chandigarh.
By train
Nearest railway stations are
Chandigarh (Station Code: CDG, 13 km from IISER)
Ambala (Station Code: UMB, 50 km from IISER)
Mohali (Station Code: SASN, 2 km from IISER): There are very few connections to Mohali. One useful connection from Delhi is Una Jan-Shatabdi (Train No. 12057)
The distance between airport and IISER is about 8 kms and between Chandigarh Railway station and IISER is about 13 Kms. Mohali Railway station (called Sahibzada Ajit Singh Nagar station or SAS Nagar station) is just 2 km from IISER.
From Airport/Chandigarh Railway station to IISER: Take a taxi/auto to IISER Mohali. Ask them to drive to IISER (pronounce it as 'eye-sir'). Almost all the drivers know the location and the way to IISER, which is situated at the point of intersection of Purv Marg and Airport Road. The road one takes while going to Mohali from Tribune Chowk is Purv Marg. Neighbouring locations are Indian School of Business (ISB) Mohali and National Institute of Pharmaceutical Education and Research (NIPER) Mohali.