US citizens and most EU nationalities require entry visa to Russia. Most South American nationalities are exempted for 90 days. Please check the following website or with your relevant Russian visa issuing office for your nationalities requirements https://en.wikipedia.org/wiki/Visa_policy_of_Russia.
Sibwaytour LLC provides an invitation for tourist visa (also known as visa support letter).
Invitation will be ready within 1 working day from providing all necessary information (passport copy, home address).
Price of visa invitation is 30 Euro.