The Masjid al Aqsa is the second house of prayer established on earth:
Abu Dhar {RA} is quoted as saying, I asked the beloved Prophet Muhammad {peace be upon him} which was the first mosque on earth? ‘The Sacred Mosque (in Makkah),’ he said. And then which, I asked? ‘Masjid al Aqsa,’ he said. I further asked, what was the time span between the two? ‘Forty years,’ the Prophet {peace be upon him} replied.
Saheeh Muslim
نسـأل الله العظيم أن يجمع المسلمين ليفك الحصار على المسجد الأقصى