Thornhill Mayne Memorial is a striking British-era building in Company Garden. It once housed the legislative assembly when Allahabad was the capital of the United Provinces, and later became part of the city's public library life.
The building is worth a look for its Gothic revival arches and red sandstone presence. Combine it with Anand Bhavan, Chandra Shekhar Azad Park, and the Allahabad Museum nearby.