placing an ad in the parliament or commision buildings

No, you can't pin ads up anywhere in the buildings - you would need to contact someone who works there and they can put your ad on the small ads. Strictly speaking they aren't supposed to be used for services, but I bet they'd turn a blind eye to piano lessons.

It might be lore useful to put your ad on the public spaces at the European schools e.g; entrance to the car park. etc