To avoid any confusion regarding mosques and its name, visit the following links which are the three earliest mosques at Madina as per Islam's history, and are very well known;
1. Quba Mosque ( http://en.wikipedia.org/wiki/Quba_Mosque )
2. Masjid al-Qiblatain ( http://en.wikipedia.org/wiki/Masjid_al-Qiblatain )
3. Al-Masjid al-Nabawi ( http://en.wikipedia.org/wiki/Al-Masjid_al-Nabawi )
Masjid_al-Qiblatain, >> it uniquely contained two prayer niches (mihrabs). Recently the mosque was renovated, removing the old prayer niche facing Jerusalem and leaving the one facing Mecca.