Storing luggage while on a Stop over in Cologne

Yes there are luggage lockers at the station (assuming you mean Hbf).

Are they the automatic ones or do you actually get a key or give it to a person? Thanks for the information.

There are both types, and in addition there is a conventionally operated luggage storage (open 6:00-22:00).

Thanks so much

So Ashley, no problems getting youluggage back? How long did that take? Thanks
Any suggestions on things to do during our short 4 hours there?

Well, Rick uses them. 1:08 in the following clip.
https://www.youtube.com/watch?v=sJ-ZQTEs-98

Of course visit the Cathedral right outside the Hbf. I don't know if you'll want to climb the tower, it is a long way up. Also a walk onto the Hohenzollern railway bridge over the Rhine. You probably crossed it entering the station on the train, or will when you depart.

I like to stop in to Papa Joe's Biersalon in the Altermarkt for a Koelsch, maybe a bite and use the animatronic jukebox, Tuennes & Schael.
https://www.youtube.com/watch?v=Nq04m02pXY0

I lived in Cologne part-time 3 different years in the last 5. I know this city well. I was connecting train there last week and wanted a few hours to re-visit the cathedral and shop a little. I had near 4 hrs.

Last week was the first time I used the automatic locker and had to asked for DB personnel's help. I first watched a German lady ahead of me going thru steps per instruction on the screen and could not make it work. I watched her went to the next locker booth and still can't get it to work. I decided to look around for the old-fashion lockers but did not find them, so I went back to the automatic locker area and flagged down 2 DB personnel walking by. It took them under 10 seconds to get me to the deposit money step. I choose 3 hr for 3 Euro, and put in 3 one euro coins, but the machine showed that I only put in 2 Euro. Luckily I have an extra euro on me. After the payment is received, the locker booth door open and the screen instructed me to put in my luggage. It went in and a ticket was issued. When I went to pick it up, I put the ticket into the slot, and it took several minutes for my luggage to come out. Both times I was in the locker booths area, I saw several people struggling to use it. Be sure to have 5 one Euro coin on you, deposit one coin and wait for the screen to acknowledge receipt of 1 euro BEFORE you put in the next one euro coin. I put in my 3 coins in rapid succession and the machine only counted 2.

If this is your first time in Cologne, 4 hr is plenty of time to see the few old buildings b/c the city was 95% destroyed in WWII. Do a google image search of "Cologne 1945". I find the post war rebuild portion of the city ugly, but my architect friend who worked for Renzo Piano find many buildings beautiful. Cologne's magnificent cathedral is a major pilgrimage stop (remains of the 3 Wise Men) and the most popular tourist destination in Germany (over 6 million visitors a year, compared to 7 million for Eiffel Tower). The cathedral offers English guided tour. https://www.nrw-tourism.com/a-cologne-cathedral -- If you want the photo on the top of this web page, you should first visit the cathedral, then walk to the back side of Ludwig Museum, walk a bit on the water front if the weather is nice, then walk across the bridge to get this arcoss-the-river shot. (round trip on bridge back to cathedral: under 30 min)

If you want to spend an hour or so in museums within 5 min walk from Hbf -- Kölnisches Stadtmuseum has the entire history of Cologne to the present days, good English info sheets available. Many students work there as explainer. They speak good English. It's a small but excellent museum housed in the lovely medieval Zeughaus.
NS-Dokumentationszentrum (info in English, creepy former Gestapo prison, https://museenkoeln.de/ns-dokumentationszentrum/default.aspx?s=315). Both museums are only a short block apart.

Cologne was an important town in Roman time. Several Roman sites scattered about the city. The small Romano-Germanic Museum next to the Cathedral is quite good. Takes under 1 hr to visit.

If you'd like a hearty sit-down meal of local specialty, try Himmel un Ääd (a dish dating back to the 18th century) and Kölsch (beer). My friend and I had a good recent meal at Früh am Dom (3 min from Cathedral in the shopping area, Am Hof 12-18). Good atmosphere/decor/food/beer/price, and fast service. Under 10 min walk back to Hbf.

Inexpensive local-specialty souvenir I buy for friends is the famous 4711 Eau de Cologne. https://en.wikipedia.org/wiki/4711. You can pick them up from the shop with huge green sign "4711 Original Eau de Cologne" diagonally across from Cathedral entrance (on Domkloster shopping street, across from Swarovski store). The big Merzenich bakery/pastry shop next to Swarovski is a local favorite.

Thank you so much for the information, This will be our first visit. Have found that perhaps some of my early ancestors lived in the area before immigrating to Russia. We are stopping to see the Cathedral on our way to Amsterdam. So appreciate you taking time to share the information. I am wary of the automated luggage storage.

There is Left Luggage office ( Gepäckaufbewahrung) located on this map. Blue block near the East exit on the Dom side.
https://www.img-bahn.de/s3/prod/v/img/stInfoPlan/8000207.pdf