The oldest mosque ever built was the Masjid al-Quba. Quba used to be a village not far from Medina.It was built right after hijra, which is the emigration of the Prophet Muhammad and his followers to the city of Medina in 622 CE. The Prophet and his companions helped building it.
The Quba Mosque has been renovated several times by various caliphs in history. The third caliph, Othman ibn Affan, was the first to do so, followed by the caliph Omar bin Abdul Aziz, who ordered the construction of the first minaret. Abu Yali Al-Husaini built a mihrab (a wall in the mosque that indicates the praying direction). During the reign of the Ottoman Empire, a few other changes were made.
Some thirty years ago, the mosque was changed once more. The construction began in 1984. Two years later, the extended mosque opened. The north side of a newly installed inner courtyard with several entrances was reserved for female visitors.
In the meantime, the mosque has expanded to a super-mosque fully equipped with four minarets, 56 domes and adjoined to it is the residence of Imams and muezzins. There is also a library and a shopping centre.
It seems to me that this mosque is definitely worth paying a visit!