No, it's part of the voltage doubler. Used to get over 200V HT (B+) from a 127V supply.
You can't use an ordinary electrolytic. The results will be messy.
I would use a motor run capacitor such as this:
https://www.amazon.co.uk/200uF-Capac.../dp/B07Q7XRV54 I presume that internally this is a pair of electrolytics connected in anti-series as a previous poster has suggested.
Alternatively I'd rewire for a conventional rectifier arrangement and run from a 230V supply. In the UK and Europe this is the easiest answer. In the US you'd need an autotransformer to step up the line voltage from 120V to 230V.
Since the OP is in Spain and the mains voltage there is 230V then if he sticks with the original circuit he would need a 230V to 127V step down transformer.
Historical note: While Europe now universally uses 230V, some European countries used lower voltages in the past. These included Spain and Belgium.