The Heidelberg Catechism was named after the city in which it was compiled and was published in Heidelberg Germany in 1563. The Heidelberg Catechism was quickly embraced by the Reformed Protestants and has been an enduring means by which thousands have been taught biblical doctrines of the Christian faith.
This application can assist you in learning the catechism and Protestant Reformed Christian doctrine. You can track your progress as you learn, study, and memorize the catechism questions and answers.
A quick comment on the graphic I picked for this application: the picture comes from Pilgrim's Progress by John Bunyan. This seemed to me a nice illustration of what is depicted in question 3, "From where do you know your sins and misery? Answer: From the law of God."
May God bless you in your study of His word and, if He has not already, may He awaken you to your woeful state and show you how you too can be delivered from your sin and misery and come to know what your only comfort in life and death truly is. :-)