I haven´t played the game in years but I think you don´t need a sword to get into anywhere in the game. Could you be more specific about the place you want to get into? A screenshot would help.

Figured it out, sort of.

You do use swords to activate mechanisms to open doors in multiple places throughout the game. I'm not sure exactly which sword needed to be found for the Proving Grounds, but I did find a sword I had missed near the Ice Path, and was able to use that to open the door to the Proving Grounds.

I won't give too much away, but the Proving Grounds was is a fairly short section of the Highpoint caves. It's unique in design, but not too difficult. It had 2 high value secrets in there.

Worth going to, imo.

You´re right, I totally forgot about them. It's obvious that I haven't played this game in a really, really long time. Glad you figured it out.