The first thing that comes to mind is Kamchatka and the Kuril Islands. These two regions are home to more than 8% of all active volcanoes on the planet. But volcanoes are actually scattered throughout the country. You can see a dormant volcano and climb it:

📍On Lake Baikal. More precisely, in the Tunka Valley, which is an extension of the Baikal Rift Zone.
📍In the Caucasus. For example, north of Elbrus, in the area called Pyatigorye. And, by the way, Elbrus itself is a dormant volcano, which last erupted 1,500-1,700 years ago.
📍In Yakutia. The most famous Yakut volcano is Balagan-Tas in the Momsky Range.

There are also volcanoes in Karelia—though they are very ancient, and now they are simply craters in the ground, usually filled with water.