Armenia is probably the least visited of the Caucuses. It has been ranked as second worst economy in the world, but it is also the first Christian country in the world. It may be hard to see at first, but as poor as Armenia is they have all made do. The capital of Yerevan is much prettier during the night than during the day. Matter of fact, you won’t really see many people during the day while the streets will be buzzing way into midnight.
Many places are open 24 hours and the cities are relatively safe. It is important to not mention the word “Azerbaijan” as it often makes people recoil. The Yerevan underground scene is under the main pedestrian avenue across from the Opera house. Outside of Yerevan there aren’t any big and bustling cities. The northern portion is mountainous and green. The southern is dry and at an extremely high elevation.
To the west lies Turkey, whose border is closed (although there has been a lot of construction in anticipation of the border reopening). To the east lies Nagarno-Karabakh which is a defacto independent country of Armenians occupied by Armenian troops although Armenia does not recognize them as a country. The only access there is via Gori, although you could hitch a ride with a military truck and they can get you through another border.
Armenia can be unbearably hot, although the south gets relatively cold. Armenians are really nice and love to show visitors around. Often you will get invited to join for dinner and drinks, remember it is rude to decline. There is a daily “overnight” train from Tbilisi, in the summer it starts from Batumi (then to Tbilisi). It leaves at 9pm-ish and is identical to the other soviet era trains like Baku-Tbilisi. The train is horrible to be honest. You will constantly be woken up for checking out of Georgia and then checking into Armenia. You will get little sleep and will have to leave the train at the Armenian border to buy your visa and get stamped. The marschrutka, on the other hand, is very frequent and very fast. You also get to use the fancy new border facilities.