Antwerp is easily accessible from Brussels in about ~1 hour by train or ~40 minutes by bus. Compared to Brussels, Antwerp is small and charming.
I would recommend starting the day with Legends of Antwerp tour. One great thing about this tour is that you get to see both a church and a museum for a short time for free. Both of these have entry tickets otherwise.
This statue of a man throwing the hand of a giant (who used to demand tribute and punish sailors if they didn’t pay) into the sea gave the name to Antwerp. “Hand werpen” means “to throw a hand” in Dutch.

Under the Scheldt River, there is a tunnel for pedestrians and cyclists. It is the only tunnel where I have seen a wooden escalator.

You will also see the statue of Lange Wapper, a giant who used to scare drunk people by growing in size.

And it is hard to miss the Nello & Patrasche Statue near the Cathedral of Our Lady. It is from a British novel, A Dog of Flanders, which, forgotten in Belgium, is really popular in Japan.

I would recommend taking the river ferry from Antwerp to Lillo. It costs 4 euros (one-way) and a 6-euro round trip. The one-way journey is about 1 hour. And you see great views on the Scheldt River along the way.

I did a small hike in Lillo. Spending 30 minutes to an hour is worth it here.

Note
- Eurostar Supermarket has great Indian food and groceries. It is run by people from Nepal.
- A day or two is more than enough for Antwerp.
