On the west bank of the river is the Staré Město (Old Town), a maze of streets where it is easy to get lost.
Those that lead down to the bridge are mostly lined with souvenir shops and can be very busy, but away from there, particularly in the area around the old vegetable market at Ovocný trh, there are some very pleasant quieter areas.
Old Town Square
Wikipedia Article https://en.wikipedia.org/wiki/Old_Town_Square_%28Prague%29
Orloj (Astronomical Clock)
The most crowded area is, of course around the Staromestká radnice (Old Town Hall) and its famous astronomical clock the Orloj.
The clock is in three sections: at the top is the most recent section containing the figures of the 12 apostles added in 1865-1866. Once an hour, on the hour, the doors open and each of the figures appears in turn and blesses the city. This attracts large crowds who probably go away feeling slightly disappointed; I know I did.
At the bottom is the calendar dial added in around 1490. this shows the day, date and month together with 12 panels depicting the passing of the seasons.
In the middle is the oldest section which dates back to 1410, the astronomical dial. It's very pretty but, you know, try as I may, I can't make head or tail of it.
On the west side of the Old Town Square, is Kostel sv Mikuláše (St Nicholas Church), the interior of which is well worth viewing. For a start it is much taller than it is long, creating a very unsettling space.
Then there is the fact that the seating is laid out like a protestant church with an emphasis on the preaching of the word, and the altar relegated to a minor role. This contrasts strongly with the flamboyant Baroque style decorations dating from 1730s.
This is because since 1920 the Church of St. Nicholas has been a Hussite Church, named after Jan Hus, a theologian and lector at the Charles University. In 1402, Hus began preached sermons on reforming the Church inspired by John Wycliffe. He was eventually burnt as a heretic in 1415.