Many people visit Kutna Hora as a day trip from Prague, and that is an easy option - there's a direct train to the main Kutna Hora station near the Cathedral of our Lady at Sedlec, from where you can get a local train to the Kutna Hora mesto station in the historic centre (or just walk the 30 minutes). However, I would recommend at least staying overnight. There's more than enough to fill your time, and the city is much more pleasant in the evenings when the tourist crowds have gone (particularly in the summer months).

The two main churches in the World Heritage Site listing are quite different but impressive in their own ways. I preferred the Church of St Barbara with its paintings on the walls and the ceiling. The Cathedral of Our Lady at Sedlec is brighter and with less decoration, but it radiates a warmth inside and feels larger than it looks from the outside.

In the historic centre, I would recommend visiting Hrádek (Little Castle) that now houses the Silver Museum; the Italian Court, which has several exhibitions about the role the building has played in the city's history; and the Stone House, with a small museum about life in Kutna Hora. There are also lots of medieval houses with interesting facades and, although the centre is not large, it's easy to spend the whole day seeing the sights and visiting the museums and churches.

One of the most popular attractions in the city, the Sedlec Ossuary, is not actually part of the World Heritage Site, but is certainly worth visiting. Thousands of human bones have been arranged into eerie art pieces and it's quite a sight. I arrived just as it was opening and had it to myself (which makes it even creepier).

This is certainly a Czech WHS worth visiting, and the fact it's so easy to reach means there's really no excuse not to.