Historians debate whether or not the ruins of Qohaito were once the inhabited walls of the ancient town of Koloe, a settlement that predated, but grew to commercial importance during, the Aksumite kingdom. Even if it wasn't, the city's impressively large remains – covering an area of 2.5km (1.5mi) by 15km (9mi) – are testament to its once-great stature. Though only about 20% has been excavated, it'll still take you a few hours to make it through the main sights.
The four columns and assorted rubble of the Temple of Mariam Wakiro are thought to have begun life as a pre-Christian church, and are surrounded by the dusty remains of half a dozen other temples. To the north of here is an underground, sandstone-hewn Egyptian Tomb, so named not because its Egyptian origin has been conclusively proven (leading theories have it as Ottoman-era) but because of the tomb's impressive dimensions.
A short walk from Qohaito takes you to the edge of a vast canyon that plummets dramatically to the ancient road to the once-important port city of Adulis to the east. On a clear day it offers phenomenal views. Near Qohaito are several rock-art sites, including the cave of Adi Alauti and another shelter with over 100 painted figures.
Though there's no admission fee, a permit from the National Museum is mandatory – as is on-site guide Ibrahim who lives in the upper village of Qohaito and expects a gratuity for his time. Nfa200 or so is suggested.