Multics (Multiplexed Information and Computing Service) was an early time-sharing operating system for mainframes and minicomputers which has influenced every operating system created since, especially via Unix (the name of which is a play on words of Multics!).
Multics is dead. There are no systems running it today (the last one was shut down in 2000.
There is however now a working SIMH-based emulator for the Multics DPS-8/M hardware, and with most of the source code still extant, it is now possible to experience the Multics computing environment.
Porting Multics to alternative hardware would be a worse-than-Herculean task. The design isn't well-suited for porting. It used specialized hardware built especially for it, this hardware had many features which do not have exact analogues on any other platform today. In addition, the word length of the machine (18-bit half-words) is explicitly included in many variable declarations in every source module.
Even if that could be overcome, Multics was written in PL/I. There are no PL/I compilers available other than commercial ones aimed at large enterprise systems, and which aren't getting any cheaper. The lack of a free Unixland PL/I compiler inhibits any porting task.