Kotayk' is one of the provinces (marz) of Armenia . It is in the centre of the country. Its capital is Hrazdan. The name Hrazdan is derived from the Middle-Persian name Frazdan. Farzdan is connected to the Zoroastrian mythology.It is the 4th town in Armenia by its population and during the Soviet years it was one of the highly-industrialised towns of the Armenian Republic. It is also home to the highly frequented tourist destinations Garni and Geghard.

Garni ("Գառնի" in Armenian) is a village in the Armenian province of Kotayk', situated approx. 32 km southeast from Yerevan, notable for its fortress complex. As it lies on the road to the well known monastery of Geghard (further 7 km southeast) it receives a large number of visitors. In the 3rd millennium BC the first fortification was constructed on an easily defendable terrain at one of the bends of the Azat river. It was conquered in the 8th century BC by the Urartian king Argishti I and the site became a military base and the king's summer residence. Several additional buildings were constructed since then, such as the king's palace, baths and the site's most famous and best preserved building, a Parthenon like temple. Of particular interest is the bathhouse, located in the northern part of the site which has a preserved heating reservoir. The interior floor is decorated with a colour mosaic with depictions of Greek mythological figures, such as Tethys. One of the intact inscriptions in Koine Greek reads: ΜΗΔΕΝ ΛΑΒΟΝΤΕΣ ΗΡΙΑΣΑΜΕΘΑ ΚΑΝΕΝΑ ΝΕΚΡΟ ΔΕ ΜΑΣ ΕΔΩΣΕ Η ΘΑΛΑΣΣΑ ΟΥΤΕ Ο ΩΚΕΑΝΟΣ (We receive no dead from the sea neither from the ocean).

The temple was constructed in the 1st century AD by the King Tiridates I of Armenia and probably funded with money the king received from emperor Nero during his visit to Rome. The temple was most likely dedicated to the Hellenistic god Mithras. The roof is supported by 24 columns with Ionic capitals and Attic basements. Unlike other Greco-Roman temples, it is made of basalt. In 1679 it was destroyed by an earthquake. Most of the original pieces remained at the site until the 20th century, allowing the building to be reconstructed between 1969 and 1979. In recent years another theory arose among some archeologists. They claim that the temple was actually constructed as the tomb for an Armeno-Roman ruler, probably Sohaemus. In that case it should have been constructed around 175 AD and thus about a century younger than indicated by the first theory. After the adoption of Christianity some churches and a katholikos' palace were also constructed at the fortification site, but these are now in ruins like most of the other buildings except the temple. Other sites of Garni outside the fortification site include churches of Mother of God and St. Mashtots as well as ruins of the Havuts Tar monastery several killometers south east from the village.

The monastery of Geghard ("Գեղարդ" in Armenian) is a unique architectural construction in the Kotayk province of Armenia, being partially cut into the rocks of the surrounding cliffs. It is listed as a UNESCO World Heritage Site. While the main chapel was built in 1215, the monastery complex was founded in the 4th century by Gregory the Illuminator at the site of a sacred spring inside a cave. The monastery had thus been originally named Ayrivank, meaning "the Monastery of the Cave". The name commonly used for the monastery today, Geghardavank (Գեղարդավանք), meaning "the Monastery of the Spear", originates from the spear which had wounded Jesus during his crucifixion, allegedly brought to the monastery by Apostle Thaddeus, and stored amongst many other relics. Now it is displayed in the Echmiadzin treasury.

The spectacular towering cliffs surrounding the monastery are part of the Azat river gorge, and are included together with the monastery in the World Heritage Site listing. Some of the churches within the monastery complex are entirely dug out of the cliff rocks, others are little more than caves, while others are elaborate structures, with both architecturally complex walled sections and rooms deep inside the cliff. The combination, together with numerous engraved and free-standing khachkars is a unique sight, being one of the most frequented tourist destinations in Armenia. Most visitors to Geghard also choose to visit the nearby Garni temple, a Parthenon-like structure located further down the Azat river. Visiting both sites in one trip is so common that they are often referred to in unison as Garni-Geghard.

Kotayk is also the name of Armenia's world renowned beer.