ISI Kolkata is a very good mix of the old school and modern infrastructure. There are classes that have a typical old-school vibe like a tall ceiling, fans hanging from rods, typical old wooden benches and desks, a traditional wood-lined blackboard with chalks and dusters.
There are fully air-conditioned classes, gallery-type classrooms and all other modern facilities you will ever need. The campus is lush green, close to the River Hooghly and thus cool winds blow throughout the day. There are open areas for playgrounds, ponds along with the hostels and the academic blocks.