The Universe is really massive. The Universe may have a limit, or it may be infinite. No one really knows. What we do know, is that there is a limit to how much we can see. This is called the Observable Universe.
Based on current estimates, and the rate of expansion of the Universe, the Observable Universe is believed to have a diameter of about 880 sextillion kilometres, which is 880,000,000,000,000,000,000,000 kilometres, or 547,000,000,000,000,000,000,000 miles (547 sextillion miles)! Now that's really big.
The heavens declare the glory of God; the skies proclaim the work of His hands. Psalm 19:1 (NIV).