Here a few web site, that you can book opera ticket via these web sites

1-) Italian operas and theather ticket

2-) England operas and theather ticket

3-) Vienna operas and theather ticket

4-) Paris operas and theather ticket

5-) New york opera and theather tickets

6-) Zurich opera and theather tickets

7-) Amsterdam opera tickets

8-) Barcelona and Madrid opera tickets

9-) San Diego opera tickets

10-) Russian opera ticket

11-) Tokyo opera tickets

madrid opera hotel paris and  Pavillon Opera Bourse, you should see these hotel, if you visited paris