Back in my Marathon running era ( 83-89 ), i lived in Shoebury which is a flat as a pancake. Hill's are hard work, but they def improve your endurance stamina.
I used to do 2 hill sessions per week. The easy one was running from my home in St.Andrews Rd Shoebury, along to Woodgrange Drive, then turn right & run to the top of the slope/hill by what's now called The Walnut Tree, & back down again to the railway bridge. Repeat 6 times & then run back to Shoebury.
The hardest one was driving to Westcliff, & parking before the Cliff's Pavilion. Then rundown to the seafront, heading towards the Pier, & about 70 yds before where the place was that burnt down, there was a path which headed up to the top of the Cliffs to where the Cliff lift started.
It was a long climb, but i'd do the same thing. 6 climbs up, 6 down & then run back to my car & drive back to Shoebury!.
Only bad memory i have, is when running up that long slope one day, head leant forward, a wasp ( for what-ever reason ) decided to sneak down the gap between my vest & neck, & sting me twice!.
I had to knock on the door of one of the houses opp the Bandstand, to ask for medication!.
Believe me, hill's are hard work, but they pay dividends. I still go up the steps opp Leigh Station 4 times per week!. Now 63, dont try to run up them, there's 180 of them & those days are long gone!. But walk up them at a good pace, & when i get to the top usually have to push my lungs ( what's left of them! ( back down my throat!.