温泉について

Two Sundays ago, I could relax really well.

～That's because I went to an onsen. <- "Onsen" is Japanese
◯ That's because I went to a hot spring. <- "hot spring" is English, and America even has some!

The hot spring was a new one in Musashi-koyama. It had two kinds of water, one of which was kind of beige. Someone told me:

× Kanto area hot spring have brown color.
◯ Hot springs in the Kanto area have brown water.

As for the best verb to use with hot springs, it's a bit hard because Americans don't have the habit of enjoying hot springs. We could say:

～I soaked in the hot spring. <- people will understand, but...
◯ I bathed in the hot spring. <- this is probably better.

There are some interesting facts about hot springs here:

http://en.wikipedia.org/wiki/Hot_spring

Even more interesting is this page on the therapeutic uses of hot springs:

• therapeutic 【形】治療法｛ちりょうほう｝の、治療（上）｛ちりょう（じょう）｝の、療法｛りょうほう｝の、癒やす力のある、癒やし系の、心の健康｛けんこう｝に良い◆「心を癒やす」という意味と、精神医学的な「セラピー治療の」という意味の両方がある (definition from Eijiro on the Web)

http://www.eytonsearth.org/balneology-balneotherapy.php