The Samsung-made Galaxy Nexus was launched way back in 2011, and officially got updates till Android 4.3 Jelly Bean before Google abandoned it. However, alternative Android OS developer Cyanogen kept the device alive thereafter, releasing a stable Android 4.4-based CyanogenMod 11 ROM for the device in 2013.
Now, the team has released the first Android 5.1-based CM 12.1 nightly build for the Galaxy Nexus, allowing users to enjoy the Android Lollipop experience on the device. The build weighs in at around 250 MB.
You can download the nightly by heading to the Source link below. However, before you do that, bewarned that that nightly builds aren't usually stable - you may encounter bugs. Plus, as you might already know, installing a custom ROM can result in a bricked device.