the highest
The highest is an example of a superlative adjective. To find out what superlative adjectives are and how to use them, follow the link.
more information: superlative adjectives
saw
Saw is the past tense of the irregular verb see. Follow the link to listen to some examples.
more information: see
thought
Thought is the past tense of the irregular verb think. Follow the link to listen to some examples.
more information: think
did open
Notice that the past tense can sometimes be formed with did instead of using the past tense form of the verb. So you can say "The tower opened on April 27th 1904." or "The tower did open on April 27th 1904.
used to
Here used to means 'in the past'. Follow the link to find out what else it can mean.
more information: used to
let go
A garden that has been let go has been allowed to deteriorate and become overgrown.
Example: The garden was let go after his wife died.
took it upon themselves
If you take something upon yourself, you decide to do it, often without asking anyone if you should.
Example: He took it upon himself to collect the mail for the office every morning.
dreamt
We can say dreamed or dreamt as the past tense of the irregular verb dream. Follow the link for some examples.
more information: dream