What type of phrase is "a magnificent building"?

It's an adjective phrase

the sun warms our planet, and with the moon, creates the tides. the moon orbits the earth and in turn, the earth orbits the sun. because they appear to be the same size in the sky, the sun, earth and moon work together to create eclipses. when the moon is directly in between the earth and sun

the group received an extra pound of butter for christmas.

the annex was delighted to hear that we'll all be receiving an extra quarter pound of butter for christmas.