Newberry National Volcanic Monument
Newberry National Volcanic Monument is run by the National Forest Service. Most areas require either a Northwest Forest Pass ($5/day or $30/year) or an Interagency Pass ($80/year). The Lava Lands Visitors Center is about 15 miles south of Bend, Oregon on US 97. There are a couple of interpretive trails and a one-mile drive that spirals up Lava Butte to a viewpoint -- due to limited parking you need to drive a short vehicle and get a pass for Lava Butte. Trees in the lava field frequently grow in spirals, caused by the root on one side getting more nourishment than the other.
Lava River Cave, a little further south from the visitor center, is a large volcanic tube, it is about a mile from the entrance to where the cave is blocked. Almost all of it can be walked upright, only a few sections did I need to stoop. It was very busy Labor Day Sunday.
Lava Cast Forest was not busy the Friday I went. The 9 miles of bad washboard gravel road probably discourages many people. However it was an interesting mile long interpretive trail. Lava flowed around many trees and left molds where the wood was. There are a number of opportunities for dispersed camping along the many dirt side roads before entering the national monument. (Dispersed camping is not allowed in the monument.)
Newberry Caldera has two lakes in it: Paulina Lake and East Lake. Neither is close to as deep as the more famous Crater Lake. (Crater Lake is in another Caldera about 100 miles away.) The lakes did not have fish until they were stocked in 1912. Both have multiple boat ramps and motor-boats are allowed.
I stayed at the Cinder Hill Campground. Sites are $16/night, and many of the over 100 face East Lake. Surprisingly I was able to get a weak Verizon signal with my external antenna and amplifier. There were hundreds of tiny frogs hopping around near the lake.
Big Obsidian Flow is the most recent lava flow in the state of Oregon.
It has an interpretive loop trail with views of Paulina Lake. Good shoes are recommended, the trail surface is mostly mixed pumice and obsidian.