The Visconti Castle (Castello Visconteo) is a medieval fortification at the edge of Locarno's old town, dating to the 12th century and substantially rebuilt in the 15th century under the Milanese Visconti family. It is best known historically as the site of the signing of the Locarno Pact in 1925 — the agreements that temporarily secured Germany's western borders and briefly made Locarno the symbol of European reconciliation.
Today the castle houses the Civic and Archaeological Museum of Locarno, which contains an excellent collection of Roman glassware, the finest in the canton of Ticino. The museum also holds medieval artefacts and exhibits on local history. The castle courtyard is pleasant to walk even when the museum is closed, and the towers provide good views over the old town.