这个计划一开始的设想很理想，但实施起来并不容易。

Zhè gè jìhuà yì kāishǐ de shèxiǎng hěn lǐxiǎng, dàn shíshī qǐlai bìng bù róngyì.

The original idea of this plan was ideal, but it is not easy to carry out.

请大家大胆设想，提出你们对未来城市的想法。

Qǐng dàjiā dàdǎn shèxiǎng, tíchū nǐmen duì wèilái chéngshì de xiǎngfǎ.

Please feel free to imagine boldly and present your ideas about future cities.

很多问题在真正发生之前，我们根本无法设想。

Hěn duō wèntí zài zhēnzhèng fāshēng zhīqián, wǒmen gēnběn wúfǎ shèxiǎng.

Many problems are impossible for us to imagine before they actually happen.