Central Yerevan is small enough to walk almost everywhere — the area from Republic Square to the Opera and the Cascade is no more than 20 minutes on foot. For anything further out, the cheapest options are the minibus marshrutky that crisscross the city for a flat fare, and the small one-line Yerevan Metro, opened in 1981, which runs north-south through the centre and is useful for the Republic Square / Yeritasardakan / Marshal Baghramyan corridor.
Taxis are cheap and ubiquitous; the GG and Yandex apps both work well and are the standard way to get around for visitors. Drivers are usually friendly but rarely speak English — having the destination written in Armenian or Russian helps.