The old town climbs the hillside above the modern city centre in a tight grid of medieval lanes, and the Ring — the central arcaded square — is its heart. The City Church (Stadtkirche) at the top of the Ring was built in the Gothic style between 1451 and 1470 and is one of the finer late-medieval churches in the canton of Bern, with good stained glass and a Baroque organ. The clock on the tower has been ticking since the 16th century.
The surrounding lanes of the old town have their medieval streetscape largely intact — not perfectly preserved in the Swiss manner, but genuinely lived-in, with the mix of languages (German and French, sometimes in the same sentence) that characterises Biel's bilingual identity. The covered arcades on the Ring's ground floor shelter small shops and cafes that are worth exploring. The whole old town is walkable in an hour, though you'll want to slow down and sit somewhere.