Foreign properties and the income from them must be declared in the Swiss tax return. They are not taxed directly in Switzerland, but they are decisive for determining the progressive tax rate.
E.g. You own a flat in Argentina with market value ARS 10 000 000 and you have to fulfill your tax declaration in Freiburg. Exchange rate as of 31.12.2019 ARS/CHF = 0.016173.
So the market value in CHF = 0.016173 x 10 000 000 = 161 730
Eigenmiewert in Freiburg = market value x 2.5 %, CHF 161 730 x 2.5 % =CHF 4 043
Be a good boy and Santa will bring you a present. 😄