Mosques are places where the followers of Islam worship. There are many of them around the world, ranging from very large Mosques that can seat 50,000 people to ones so small that they can only hold 10 people at a time. They are known for having amazing domes with crescents on top; tall and slender minarets that are usually situated at the corner of the building structure; amazing Art of Arabic Calligraphy and Quran verses in the Prayer Halls.
Here is Most Magnificent Mosques in the World. You may have been fortunate enough to have already visited some of them. I hope you enjoy and agree with some of my picks.

Mosque of Dearborn, Michigan, USA

Shah Faisal Mosque, Islamabad, Pakistan

Muhammad Ali Mosque, Cairo, Egypt

Shah Mosque, Isfahan, Iran

Al Aqsa Mosque (Dome of the Rock), Jerusalem, Palestine

Putra Mosque, Putrajaya, Malaysia

Sultan Ahmed Mosque a.k.a Blue Mosque, Istanbul, Turkey

Sultan Omar Ali Saifuddin Mosque, Bandar Seri Begawan, Brunei

Al-Nabawi (Prophet) Mosque, Medina

Haram Sharif Grand Mosque, Mecca