Sure, here are ten useful features for distinguishing an amphitheater in a photo:

1. Circular or oval shape: Amphitheaters typically have a circular or oval shape, with seating arranged in a concentric pattern around a central performance area.

2. Tiered seating: The seating in an amphitheater is typically arranged in tiers, with each row of seats slightly higher than the one in front of it, in order to provide a clear view of the performance.

3. Central stage area: The central area of the amphitheater, which is surrounded by the seating, is typically the stage area where performances take place.

4. Elevated stage: The stage area in an amphitheater is often elevated above the level of the seating, in order to provide a better view for the audience.

5. Open-air design: Unlike traditional theaters, amphitheaters are typically open-air structures, without a roof or walls to enclose the performance area.

6. Stone or concrete construction: Amphitheaters are often constructed from stone or concrete, which gives them a distinctive appearance.

7. Colonnades or arches: Some amphitheaters feature colonnades or arches, which provide additional support for the seating areas.

8. Flanking staircases: Many amphitheaters have flanking staircases that lead up to the seating areas, which can be a useful feature for identifying them in photos.

9. Large capacity: Amphitheaters are typically designed to accommodate large crowds, with some of the largest amphitheaters able to seat tens of thousands of people.

10. Historical significance: Many of the world's most famous amphitheaters are centuries old and have played important roles in the history of their respective cultures, making them significant landmarks and tourist attractions.