Now available free, The Elder Scrolls: Arena is something of a classic and it continues to live on with thanks to the free and open source game engine OpenTESArena. Bethesda Softworks actually made The Elder Scrolls: Arena free to download some years ago as part of the 10th anniversary which has certainly helped.
Still in early development, with gameplay not really there yet, it's very promising and a big new release went up a few days ago further expanding what it's able to do with the original game data. OpenTESArena 0.11.0 adds in quite a lot including: original entity loading (static NPCs, creatures, trees, furniture, palace rulers, etc.), lights, water and lava rendering, fading voxels, translucent entity rendering, Ray Cast selection with pixel-perfect option and more.
Projects like this are vitally important. Some games really are true classics, loved by many, and deserve to be experienced by a new generation of gamers in an updated form. Gaming is part of our culture and history, and a shame when some older gems get left behind by all the shiny new games coming out all the time. It's why projects like this and OpenMW, OpenRA, openXcom and more are so important.
See more about it on GitHub. All the instructions are there to get going with it, although as mentioned it's going to still be a while before it has some proper gameplay but you can at least walk around and explore for now.