Possible Clues:

• A street, ornate, in dull European city
• Mum's taken for a ride, we hear, in Dutch city
• Dutch provincial capital, the location of the Bonnefanten fine arts museum
• Capital of the Limburg province of the Netherlands
• City in south-east of the Netherlands
• European Community treaty setting out the terms for the creation of the European Union
• A thoroughfare rolling through endlessly dull European city
• Nineteen-hundred and ninety-one EU treaty city
• Dutch city, treaty