A few kilometers away from the Trass caves in the Brohltal is the Laacher See volcano, which filled the surrounding valleys with lava particles up to 60 m high when it erupted 13,000 years ago.
Clara Viebig, the poet who is close to nature, was so impressed by the Maars in the Vulkaneifel that she made them unforgettable as "Eyes of the Eifel".