Gorely
(1.829m max. alitude, 900m gain, 5-7 hours)

The Gorely volcano is the easiest to climb of this gang of four. It can be reached from Petropavlovsk about 4hours via a reasonable road (in summer time). It is a freestanding volcano with relatively gentle slopes. It takes about 3hours to reach the top. There're two craters - the first one is inactive and houses a blue glacier lake whereas the 2nd crater is still active with several fumaroles and volcanic steam around the lower crater rim. You should do a full circle around the crater here for the best experience. You return on the same route again.

Avachinsky
(2.750m max. alitude, 1900m gain, 6-9 hours)

The Avachinsky is one of two major volcanoes in the immediate vicinity of Petropavlovsk. The access to the trailhead is fairly unusual via a semi-dry river bed (in summertime only) - it's a bumpy ride and takes about 2-3 hours from Petropavlosk. It is a fairly short but steep ascend to reach the top of the volcano. After crossing a glacier river you climb up a long ridge for about 2-3 hours. The last part up a the final cone can be very strenuous due to the loose ash ground. On the top you'll find a steamy (black) lava pan - the whole crater is filled similar to a popcorn bag. You cannot circle the crater because the lava is floating over the rim on one side. On the way back (and up) you should have great vistas of the Karymsky volcano unless the weather thinks otherwise. You return on the same route again.

Mutnowsky
(2.328m max. alitude, 800m gain, 8-10 hours)

The hike to the Mutnowsky crater is a long one. You start at the nearby geothermal power station (~4 hours by car from Petropavlovsk) and do a half-circle around the volcano to reach the open entrance to the inner crater - you don't really climb up to the top although there's a bit of an altitude gain to manage. There're no major obstacles - only some fairly long passages on snow (depending on the season naturally). You should have good vistas of the Gorely volcano on the middle section of the trail. The crater is very active with lots of sulfur fumaroles which can get quite nasty because you've to step through some steam here (and sulfur steam + humidity = sulfur acid ...). A really cool feature is the glacier floating straight into the crater. At places you can observe how the ice is evaporating by the hot ground! You return on the same route again.

Tolbachik
(3.085m max. alitude, 1400m gain, 7-9 hours)

The Tolbachik volcano is located in central Kamchatka about 550km to the north of Petropavlosk. The final 50km require an off-road vehicle due to the bad "road" conditions and the loose volcanic ash once you reach the primary volcanic zone. It is possible to reach the trailhead at around 1700m by 4x4/truck. From here on you traverse a volcanic plateau with rather gentle slopes for about an hour or so. Thereafter it is another two hours across some moraines before reaching a small high plateau. The final portion is a steep ascent along a more or less icy/snowy ridge up to the crater rim. The crater (inactive) is about 400m deep and from the rim you should have great vistas of the "sharp" Tolbachik peak (the crater top is called "flat" Tolbachik) and the volcanic plateaus below. You return on the same route again. Apart from the Tolbachik crater you should also check out the nearby chain of smaller volcanoes (~100-250m) on the lower slopes (next day). They are still partially active from their latest eruptions (1975/76).