The extravagant and brightly colored domes of the cathedral's exterior mask a much more modestly decorated and somewhat less spectacular interior. Small dimly lit chapels and maze-like corridors fill the inside of the church and the walls are covered with delicate floral designs in subdued pastel colors dating from the 17th century. Visitors can climb up a narrow, wooden spiral staircase, set in one of the walls and discovered only in the 1970s during restoration work, and marvel at the Chapel of the Intercession's priceless iconostasis, dating back to the 16th century. There was so little room inside the church to accommodate worshippers, that on special feast days services were held outside on Red Square where the clergy communicated their sermons to the milling masses from Lobnoye Mesto, using St. Basil's as an outdoor altar.