Today, the two largest ground$-$based optical telescopes on Earth have an aperture $($diameter$)$ of $10$ meters. They are:

I.

Keck and Mt$.$ Palomar observatories

II$.$

Chandra and Hubble space telescopes

III.

Great Telescope Canary Islands $($GTC$)$ and Keck$$observatories

IV$.$

Very Large Telescope $($VLT$)$and Chandra observatories