Underpass

It is 130 m long, lined with limestone and illuminated through well windows in its vaults. They say that the echo here repeats a word up to 4 syllables long. You can ask questions like: 'Who ruled here (Paul, Pavel...)', 'Which flower is not afraid of frost (Rose, Rose...)', and so on. Of course you need to say it in Russian if you want to get correct answers. Also you need to stand in a certain place in the turn to get the answer at all. Although, nowadays it’s better not to ask unnecessary questions, you’ll be safer...