I always thought so too because of movies and games. One-handed swords were only about 3 lbs, and two-handed swords, like the one she found, were only around 6 lbs. Even zweihander was under 10 lbs. Crazy.

https://workingtheflame.com/heaviest-swords-in-history/

The Lady of the Lake, her arm clad in the purest shimmering samite, held aloft Excalibur from the bosom of the water, signifying by divine providence that this little girl was to carry Excalibur. That is why she is now our Queen

I visited a museum where there you could handle exact replicas of the swords and maces they had on display. The edges were blunt and the short chains they were attached to were bolted to the stone floor, so no one could steal them or do any damage with them.

But if you knelt down, you could get the feel of wielding them in action. One handed sword was really light and even my then 13-year old son could handle the two handed one.

I had read that they weren't heavy, but I was still very surprised how light they actually were.

Nah not really. Video games try to make big weapons seem super heavy because it needs to be done for balance usually. But you don't want your weapons heavy. Heavy weapons are slow. Slow people are dead.

This is a common misconception from their depictions in the movies showing the characters treating them like hammers, both in terms of how they swing them and sometimes in terms of how they hit enemies with the blade never cutting anything.