Going to these two places over six days in late April/early May was probably the coolest trip of my time in Ethiopia. I am maintaining the minimalist commentary because I have to give my (employer-provided) computer back in under two hours, but if you make one trip to Ethiopia, this should be a part of it.
Roll 1: Tigray, northern Ethiopia. Includes the monumental 4th-8th century stellae at the ancient capital of Axum, churches of Axum including that said to hold the Ark of the Covenant, shots of the Arizona-like Tigray landscape, Debre Damo monastery which is reached by climbing a rope up a cliff (the founding saint apparently climbed up the tail of a snake), stone churches of the Gheralta cluster notable for their inaccessibility (the path basically becomes a rock-climbing expedition) and ancient paintings:
Roll 2: The Danakil Depression -- Known as the hottest place on Earth, the Danakil is also notable for its extremely active volcano, active camel-driven salt trade, and lakes of sulfur and phosphorus: