Founded in the eleventh century, Saint Sophia is the oldest standing church in Kyiv and a UNESCO World Heritage site, guarding some of the finest Byzantine mosaics and frescoes anywhere, including the shimmering Orans figure in the apse. Now a museum rather than a working church, its grounds and green-and-gold bell tower are a highlight of any visit. Buy the combined ticket, climb the bell tower for the view across to Saint Michaels, and look up at the mosaics.