Looking for things to do in Piraeus Port

There is plenty to keep you busy for at least a few hours in Piraeus, it’s not just a ferry port.
You can take a stroll around the marinas or visit the Maritime Museum and the Archaeological Museum. There is also a municipal market located just a block away from Gate E9 at the ferry port.

There are hundreds of places to eat and drink, ranging from street food spots to seafood restaurants, grill houses, and more.
Here are two I would suggets:

Aposperitis Maereio Piraeus

https://maps.app.goo.gl/pt3NWxBkVweT3ymt9

Near the marina:

Στο υπόγειό μας (In our basement)

https://maps.app.goo.gl/wWanS7tckjcR7ipL8

There is also a website dedicated to Piraeus:

https://www.destinationpiraeus.com/en

The archaeological museum houses the bronze statues that were dredged from the harbor. It is adjacent to the ancient theatre. Parts of Themistocles defensive wall are visible in the small (pleasure boat) harbor.

A second vote for the Archaeological Museum, which has some excellent pieces and is under visited. It’s then an easy walk down to the Zea Marina from which you can walk west along the front.

Or you are only 20 minutes by metro to Monastiraki and have plenty of time to go up and walk round the Acropolis.

Thanks everyone!! Now I’m looking forward to my layover in Piraeus and not dreading it!

Does anyone know where I could safely store my suitcase so I don’t have to drag it around with me?

I've never needed one myself, but there are quite a few luggage storage services at the port. I understand you've already been to the port of Piraeus a few times, so it shouldn't be a problem to find them. You can ask at one of the many ferry ticket offices or search for "luggage storage" on Google Maps around the Piraeus metro station area.