What’s worth seeing in Interlaken ?

Not much. Its got a familiar name because its a transportation and logistics hub for climbers and winter sports. Shops, restaurants, tourists. Its at the foot of the mountains but not in the mountains, so you can see them from there but you're in a flat area.

Agreed, not much.

Not a lot for sightseeing.

Near Interlaken West station is a small model railway layout. Also near there is a large Migros supermarket with cafe.

There is a small cog railway up to a lookout - in all my years going through I've never tried it.

There is the dock for the boats on Lake Thun.

There is a McDonalds, a lot of tatty tourist-trap stores and some old hotels.

There is a bus station, and occasional horse drawn carriages take the tourists around but I don't know where or for how much.

Near Interlaken Ost station, the one you need to go up to Lauterbrunnen and thence up, there is a large Coop supermarket with cafe.

There is the dock for the boats on Lake Brienz.

There is another bus station but no horse drawn carriages.

A distance away is the municipal park and swimming area.

Between the stations is the large park/field where hang gliders land (watch your head).

There are lots of houses and hotels. There is lots of traffic,

Pretty much everything worth seeing is up the hill.

OMG, Nigel! I'm nominating your post for best post ever for trying to talk someone out of a location without saying "Don't bother"!!!

Damned with faint praise as my Mama would have said.....

Harder Kulm (perhaps the lookout point you refer to Nigel?) is a nice spot - there is a restaurant up there with a large patio, good panoramic views over Interlaken, the lakes and the mountains. You can also do some hikes from there and at the base is a small, free animal park with ibex and marmots. https://www.interlaken.ch/en/experiences/mountains-panoramas/mountain-excursions/harder-kulm However, not much point going there if you are already staying up in the mountains. I've only been up there on a day trip when I was escaping the fog over the 'lowlands' because it is very easy to reach.
As others have said, Interlaken is mainly a touristy transport hub and a base for adventure sports, not really that interesting to visit itself. Hostels/hotels, tons of watch and souvenir shops, a Hooters (yes, really). There are a few nice microbreweries if you like beer. Otherwise, I'd skip it.

yes, hopper18, I was referring to Harder Kulm.

Pam, just telling it like I see it...

Lol. I wish I could mince words like that. We are staying in Wengen and it’s our last full day. Would love a suggestion on a relatively easy hike to do with partly cloudy weather which we have today.

There are plenty of fairly easy walks around Wengen itself. Most hotels or the tourist info office have a great brochure with a map and suggestions. Two popular options are Mönchblick and the Staubbachbänkli.
The webcam at Hotel Edelweiss is en route to Mönchblick and looks fairly promising right now https://bellevue.roundshot.com/#/
The Hunneflue walk (same brochure) is also good - nice views of Lauterbrunnen valley and at the end you can see the 'other side' towards Interlaken including Schynige Platte.

If the clouds thin out a bit or you just want to walk regardless, two fairly easy but very scenic hikes are https://www.maennlichen.ch/en/summer/experiences/panorama-trail.html above Wengen and https://jungfrauregion.swiss/en/summer/tracks/gruetschalp-winteregg-muerren-1h30/. (also possible in reverse from Mürren)

Link to Wengen walks including the ones I mentioned (times are one way and don't count stopping for photos)
https://jungfrauregion.swiss/en/summer/see-and-do/hiking/walks/

Hopper thx so much for that link and info

Agree that your wife will be glad you went up the mountain. Interlaken is full of touristy souvenir shops.

Interlaken is ok. A rather small city. You can easily walk it. It is much better to go up the mountain. Gimmelwald to Murren and on up to the Schilthorn if the weather is clear. Many hiking possibilities. I think the best thing to do in Interlaken is to watch the hang gliders come off the mountain and land in the big, open grassy area. There is also a nice boat ride on Lake Thun that is enjoyable. If I am coming from some distance I will often spend one night in Interlaken before heading up the mountains.

Nigel neglected to mention the Tourismuseum. If you like old travel posters and the like, it's worth a half hour.
https://www.interlaken.ch/en/experiences/poi/tourismuseum

He also neglected to mention that many of the stores seem to be jewelry stores or sex shops. There's also at least one casino (I forget if there are more).

The Migros and Coop in Interlaken are actually very useful if you need something at a reasonable price. When my day bag tore, I got a nice knapsack at Migros for 20 CHF. I still use it almost every day. I'd love to get a backup one here in the US, but they're actually more expensive!

There are many restaurants, including a "Paksitani" restaurant, which put me in the mind of Punxsutawney Phil from Groundhog Day.

Seriously, if you're not looking for any of these things, or the stuff Nigel mentioned, there is absolutely no need to go to Interlaken except to change trains, catch a boat or bus, etc.

pj64, please report back on how your day in Interlaken went.

According to the videos, there is a Hooters in Interlaken. Hopefully still open.

Check out Karl Watson videos for hiking options in the B.O.