Protected by UNESCO, Cologne's Dom is the first sight you will notice when taking the main exit from the central station. (If you don't see it, you've taken the back exit.)
If you are in good shape, take the 509 stairs to the top of the south tower. It takes about an hour, so wear comfortable shoes, but it's worth the hike.
Touring the Cathedral is forbidden during Mass. Entry into the cathedral is free but you will be asked for a donation.
Admission to the tower costs (regular/reduced): €2/€1.
Admission to the treasury costs (regular/reduced): €4/€2, however, a combined ticket granting you admission to the treasury and tower can be purchased for (regular/reduced): €5/€2.50.
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