Cities everywhere use concrete benches, sometimes with wood slats, sometimes not, because they are super durable. If it has any wood parts they would look better and hold up better if painted. But you wouldn't repaint every year. Just every few, and it would be a minimal project.

I have an iron bench bought from an ornamental iron shop in my community. It is powder coated in a wonderful dark blue and hasn't required any upkeep in the 10 years I've had it. It is not rusted or crumbled or bubbled at all. This is a true powder coating, not the cheesy finish on iron products from China. So you could explore benches from artisans in your area, too.

How about something like this:

The neighbor next door has an outdoor table made out of stacked masonry tiles with a granite precut countertop piece as the top that has been beveled on all four sides. You could do a shorter version as a bench. It requires no upkeep and it survives frosts, rain, and sun. We had a bench I dismantled that had a thick wood top for the seating portion and the support legs were open masonry patio blocks used in the 1970s to build dividing walls. I repurposed everything. I also used a downed tree trunk as a bench. It rotted and has been retired to the woods. Things change. That stone bench recommended is not going anywhere anytime soon. Great idea.

Cement is the way to go. Maintanence free...lasts forever.