Grand Central Terminal is a beautiful structure. Worth a visit and contains some interesting shops and dining as well.
Right in the middle of everything off Times Square, Tony's Di Napoli is solid family style Italian food. Large portions and reasonable prices for NYC. The do a huge pre-theater business, so reservations might be in order if you're going at that time. At lunch a table is usually not hard to get.
https://www.tonysnyc.com/
BXL Café (125 W 43rd St, New York, NY 10036), also near Times Square is a smallish bar that serves one of the best selections of Belgian beer I've ever seen, many on draft. Food is acceptable, but I go here for the beer.
McSorley's Old Ale House (15 E 7th St, New York, NY 10003). A NYC institution since 1854.
If you want interesting ethnic food, I'd vote Korean. Visit Koreatown
https://en.wikipedia.org/wiki/Koreatown,_Manhattan. Heart is located at 32nd St between 5th and 6th Avenues. Lots of good Korean BBQ restaurants, Wonjo is one of my favorites.