New Delhi, Nov. 15 -- I had no clue I lived across the street from a 100-year-old "hidden gem", a restaurant so hidden it did not even have a signboard.

I learned all that thanks to an enthusiastic Instagrammer.

Radhu Babu's teashop in south Kolkata is old but not quite 100. I did not think of it as hidden since its tea was so famous that film stars like Raj Kapoor and Uttam Kumar are known to have come there for it. The story goes that Raj Kapoor would even take its prepped fish fries and cutlets back to Mumbai where his chef would fry them for him.

Also for a "hidden" gem, it was hiding in plain sight, as it were. Our neighbour would stand on her balcony and try to peer into its kitchen to see if she could decipher what went into the...