No longer a working church, St. Sophia is the oldest cathedral in Kiev. The main church is beautiful and contains some interesting exhibits, including a few frescos salvaged from the original St. Michael's across the square. The metropolitan's house is also worth a visit. And be sure to buy a ticket to climb the bell tower (unless you fear heights) which offers the best views in Kiev. One of the top four or fives places to visit in the city. And right in the middle of town.
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